Welcome to the second part of the Bloodborne Bosswatch! With this update, we'll cover the remainder of the game's story and optional bosses. I've left out the Chalice Dungeon stuff this time, in part because the third one I went to - Lower Pthumeru, which is the third in that series - was nothing but boss repeats. I think we can safely exclude the majority of them, though maybe I'll revisit them some other time. There's enough going on with in the Chalice Dungeon system to not throw it out entirely - I was thankful that I was able to get a few more levels with a Depth 4 dungeon before the final gauntlet of story bosses - but it feels fairly inessential. I mean, it's all dungeons clearly made out of different identikit parts stuck together, and I get enough of that from Bethesda games.
Instead! We shall focus on the final ten bosses of the game. Four of which dwell in optional areas but are worth pursuing for their rewards and lore relevance, not to mention the chance to strategize one's way through another thrilling boss battle. I will, of course, set up each of these bosses by briefly describing the regions they inhabit; some of the late-game regions get really creative and weird, and I'd be happy for a chance to elaborate on them for the sake of getting my own thoughts in order if nothing else. I should state that the following interpretations of the game's story and mythos are my own, based on item descriptions, in-game notes, general context and the game's precious few cutscenes. I'll probably be off-base a few times with the general lore groupthink (or what lead designer Hidetaka Miyazaki has explicitly confirmed in interviews), but trying to piece together the game's lore for myself is one of my favorite parts of any Souls game. That also leads in to my final disclaimer: There will be Bloodborne spoilers out the wazoofor the mid- to late-game, up to and including how it ends. You have been warned. Y'know, politely. Yharnam welcomes all visitors andtheir precious blood after all.
If you're coming to this blog completely fresh you'll probably want to read Part One first. You might also be interested in reading the Bosswatch series I created for Dark Souls II as well: Part One, Part Two and Part Three.
I left off last time after the trio of serpentine guardians of the Forbidden Woods that protect the path into Byrgenwerth: a location of some lore importance, given the clues we've been finding. Byrgenwerth is said to be a school of knowledge that would eventually beget the Healing Church of Yharnam and later break off from them due to ideological differences regarding the use of Old Blood: we see a cutscene shortly after defeating Amelia that shows that the Church and Byrgenwerth parts ways over a disagreement about how mankind should fear the Old Blood when attempting to further mankind's evolution. Of course, the scene itself is a little more vague, but its meaning is expounded upon in the descriptions of various key items you find from that point onwards - in that classic Souls manner of obfuscated plot exposition. Yet, when you encounter Byrgenwerth, you see that it appears to be a shell of a building: hardly the academy you were expecting. That's because half of Byrgenwerth is no longer there: it's been transported. Transported where, you might ask?
The Lecture Halls exist between the worlds of reality and that of the nightmare: a vaguely-defined other dimensional space that gives physical form to thoughts and dreams. In essence, it's not too far detached in concept from the player's home base of the Hunter's Dream, though is far more dangerous. The Lecture Halls have two floors - though the upper floor is initially impossible to reach from the lower - and are filled with slime enemies that clearly resemble the students of Byrgenwerth. It isn't clear if these are nightmare manifestations aping the students that once filled the halls, or if they are the actual students of Byrgenwerth that were unable to hold their forms and sanity together in this space between worlds. (You ever see that Drifting Classroom manga? It's probably like that, only with less murder. Well, until you show up.) Either way, it doesn't get any less inhospitable once you leave via the front door.
The Nightmare Frontier is a region of irrational rock formations and floating islands in an endless white pocket dimension and the first truly alien location the player might visit. Unlike the rest of the game and how every location is clearly linked to Central Yharnam through one passage or another, there's nothing that might correspond to the geography of Yharnam in this place. Likewise, the creatures of this realm defy any sort of conventional humanoid appearance that would indicate that they were once people. It's not quite Xen in terms of looking like an alien planet, but it's clearly not of this Earth either. It's also very unpleasant to walk through, because between the giants hurling instant-kill boulders at you and the poisonous swamp that runs through and underneath the landmass, it takes a while to survive long enough to find one's bearings. It doesn't help that most of the landscape are just gray rocks, which ably hides many items, exits, slopes and many of the gray/white monsters themselves. Fortunately, it appears to be entirely optional: the only reason you might end up here is by following a few cryptic hints by our old friend Patches, who in this game has been transformed into a spider and is utterly in the thrall of a Great One named the Amygdala.
Amygdala, it turns out, is the name of all the giant monsters that become visible after a certain point in the game (or after a certain amount of Insight has been gained). They have just enough of a physical presence in Yharnam to pick you up and momentarily drive you insane with a damaging frenzy attack, but are otherwise largely inert. The Amygdala in the Nightmare Frontier, however, is far more active and aggressive. I wouldn't say with any authority, but I suspect the Amygdala are biding their time until they can fully transition into Yharnam and tear its inhabitants apart as easily as the beasts are doing. In fact, encountering one such Amygdala is how you end up transported to the Lecture Halls in the first place.
The boss is a real toughie, in part because everywhere except its head takes chip damage, and as a fifteen-foot-tall monster with numerous limbs it rarely deigns to lower its head into striking range. You sort of have to stay close and pick your moment to strike, hopefully stunning it sufficiently to pour on some real damage before it rises back up and becomes nigh-invincible again. While it can be unpredictable with its swatting attacks - it has multiple arms to look out for - it's when it remembers that it's a Great One with a plethora of psychic attacks that it becomes a true menace to deal with. By the later parts of the fight, you spend a lot of time running around avoiding lasers and balls of plasma: common abilities of the future Great One bosses you'll encounter. The game doesn't emphasize magic too much, even with the separate Arcane stat that you can choose to power up, but the few tools that offer the player some kind of magical attack are clearly based on the powers the Great Ones employ. It's probably fair to say that the Great Ones brought magic with them into the world of men, and the player is simply invoking that same mystic power against them.
Amygdala is a tough opponent but predictable enough in its movements, making it the sort of archetypal Souls boss fight where you might crash and burn magnificently on your first try but will quickly be able to turn it around once you know what to look out for. I think, lore-wise, the purpose of the fight is to demonstrate that a whole legion of Amygdalas would be more than enough to conquer our plane of existence with ease. For now, all they can do is invisibly hang onto buildings and swipe at anything that gets near.
Byrgenwerth is a very unimpressive stage. That isn't to say that it doesn't look as fantastic as any of Bloodborne's environments. The game has a supremely odd night cycle that moves forward based on the player's progress: that also means that while some commonly traversed areas like Cathedral Ward and Central Yharnam reflect the changes in the night sky, others appear to be locked in a static time based on when you're likely to encounter them in the plot. Thus, Byrgenwerth and the previous forest are depicted in a far darker period of night rather than the fixed twilight of the regions that came before.
Byrgenwerth essentially comprises of a single administrative building with an observatory on top, and the lake it overlooks. The rest, as we've ascertained, has been spirited away into a nightmare dimension. There's very few enemies: a handful of spider-transformation beasts and a solitary hunter NPC. The goal here, then, is to set the stage for one of the most significant and interesting story boss battles in the game.
Rom, the Vacuous Spider
Rom is a mysterious entity that, like most things Bloodborne, isn't really explained in full detail until after the fact. However, its (or her) purpose becomes clear as soon as it is defeated: it is the one anchor that is holding Yharnam back from the nightmare that slowly envelops it. This is made evident by how the world warps after Rom's destruction, revealing the Amygdalas to everyone regardless of their insight and displaying a significant number of other changes across the world. More on that in the region guide to follow.
Rom herself (the lore suggests it's a she, at least) is actually non-combatative and lives peacefully in a mirror-like pocket dimension underneath the lake; a similar environment to the Four Kings boss fight of Dark Souls. An enormous grub-like bag of flesh and eyes, she appears to be an artificial Great One: a former human turned "kin", as the Great Ones and their offspring are known, and given the purpose of protecting the rest of humanity by blinding them to the presence of the Great Ones. At least, this is what I infer from her ambivalent state and the madness that follows: she won't fight you unless you strike the first blow, and that's unfortunately what you need to do to progress. Her semi-magnanimous efforts don't become clear until after the fight in one of the game's morbid twists. In essence though, you're tearing off the collective blindfolds from everyone's eyes, and what could be more important than revealing the truth? It's too bad that there are no sane NPCs left to appreciate the gesture once Rom has been slain. Well, besides those you manage to save by sending them to the Cathedral, but even they don't seem like they have all their marbles after the big change.
As a boss, Rom has a very specific approach that most would deem an "adds" or minion boss. She has three stages based on the damage she's taken, each one increasing the amount of aggression she displays. After each phase she teleports, creating more of her spider minions, and starts firing more ice-based spells which change their pattern depending on your distance from Rom. In a twist on the usual pattern for minion-summoning bosses, the minions are the real fight here, with Rom herself being a persistent distraction that you have to be wary to elude whenever she rises up to unleash another rain of deadly icicles. Once the minions are gone Rom is a very slow and predictable opponent to cut down; however, the spiders and their obscene damage output are no joke if ignored for the sake of expediency, especially if you let them swarm you. By systematically removing them all, you make the boss fight far easier to survive. This fight, then, is designed to prey on your impatience - more so than any other boss - by taunting you to perhaps risk leaving some spiders alive and head straight for the boss for the sake of speeding things up. With enough diligence the fight is easily won. However, patience isn't always a popular virtue, especially when you're on the fourth or fifth attempt of the evening.
Yahar'Gul Unseen Village
This is actually the second time you visit Yahar'Gul, technically speaking, because it first becomes available via the Hypogean Gaol. That's an optional area and easy to miss, but the first trip through allows you to collect some high-level items. After defeating Rom and being placed near Yahar'Gul's actual entrance, you get some first-hand experience with just how badly the new post-Rom blood moon world has fared. If possible, the world has gotten even more crazy, and thanks to Yahar'Gul's governing School of Mensis, they were prepared for it. Sort of.
The School of Mensis, which will become important later, is a heretical sect of the Healing Church and the organization that leads the kidnappers of Yahar'Gul Village. While the Healing Church seeks to evolve humanity through blood ministrations, and Byrgenwerth through studying artifacts of the Great Ones and avoiding the dangerous and unpredictable results of the blood transfusions, the School of Mensis and its founders figured the best route for humanity's ascension would be to get into contact with the Great Ones directly and ask them for guidance. The Mensis scholars are obsessed with discovering a means to communicate with the Great Ones, though it appears the process either drove them mad or killed them. They've been left to their own devices until this point in the game, presumably regarded as dangerous lunatics to be avoided, yet it becomes evident in this eldritch-heavy stage of the game that their plans have had far more success in summoning the Great Ones than either Brygenwerth's dead-end research or the Church's disastrous spreading of the blood curse, which has taken almost all their lives and left the rest as mindless beasts. At this point in the game, it's clear that the School of Mensis has all the answers. It then becomes the player's task to wrangle them out from their broken minds.
Yahar'Gul Unseen Village has numerous indicators of the fallout of Rom's demise, the first and foremost being the presence of many, many Amygdala creatures hanging off of buildings. Emboldened by being out in the open, there's one in particular that will use its laser eyes to utterly devastate you from range as you try to close the distance, in what amounts to Bloodborne's equivalent of the "dragon bridge" encounter. The foes are now deadlier too: this area introduces the annoying Chime Maidens (provided you haven't met them in the Chalice Dungeons) who continually summon red-tinged enemies until they are defeated. The rest of Yahar'Gul is filled with hunters and the madwomen of the Hemwick Charnal Path: however, both have been subtly effected by the insanity of the blood moon, becoming far stronger and, in many cases, resurrecting from pools of blood after a few moments. Yahar'Gul is effectively an "oh shit" moment where the player is privy to just how messed up everything has become - though other regions remain more or less the same but for the blood moon, which diminishes this twist somewhat.
The One Reborn
The School of Mensis managed to link the existence of the blood moon to a very powerful Great One, but the creature that is pulled forth from the moon and summoned into being for this fight is either an imperfect copy of that perfect lifeform or a Great One that didn't quite, well, transition through the veil of reality properly, like that one teleported space pig in Galaxy Quest. It's a grisly mound of bodies and beasts that might well be comprised of what was left over from the now-vanished population of the village. This Not-So-Great One uses its immense physicality to keep you dancing around to avoid its swings, though at the same time it's far more sluggish than the Amygdala and the other Great One fights to follow. It can hit very hard, and shouldn't be underestimated for that reason, but an agile player should be able to exploit its attack radius by diving between (some of) its legs and hacking it apart from there.
However, the boss is both a hideous and pitiable thing and will actually use its barely held-together convergence of corpses against you in how it physically starts to collapse as you fight it. You get the sense that, even were you not actively hacking it apart, it probably wouldn't survive very long in this plane of existence. Driven by pain and madness, it launches unpredictable attacks at you and will, at one point in the fight, start raining down loose viscera on top of your head. It can also start creating pools of venomous fluids from its orifices. It's not a particularly pleasant boss, all told, and you half suspect that the legion of Chime Maidens that summoned it - who will be a constant pain throughout the battle if not removed in a similar manner to the Rom spiders - are a little aghast about what they've done.
I'd liken this fight to a mix of the Tower Knight of Demon's Souls, what with the creature's size and the surrounded walls filled with regular ranged enemies that both act as a distraction and as additional targets, and The Rotten from Dark Souls II (or the Legion boss of any given IGA Castlevania, even). It's not the most difficult fight in the game, but it's clearly one of the most unfortunate. You almost feel sorry for it.
A little detour now to a remote castle outside of Yharnam that the player is personally invited to visit. Cainhurst Castle is every bit the classic snowy Gothic fortress from Dracula: fitting, as it once hosted a legion of dapper nobles that feasted on the blood of others as a matter of course. In a world obsessed with blood and the consumation thereof, the behavior of an aristocratic echelon of bloodsuckers probably didn't seem that abnormal. Even so, they were all wiped out by a particularly determined group of hunters that called themselves Executioners, with only ghosts and a handful disturbing bloodthirsty creatures left behind to guard the estate, along with a handful of servants who protect their masters even after death.
The Castle's a great environment, and I wonder if it wasn't just thrown in for a bit of genre-apropos fun because of all the Gothic, Victorian-era blood-drinking going on elsewhere. It wouldn't have felt right to exclude such an iconic structure for this specific style of genre fiction; a chateau as eerie as it is extravagant. The female ghost enemies within, who either weep uncontrollably or lunge at you with daggers, are incredibly unsettling. More unsettling still is when you find yourself branded by one of the servants and the ghosts all start screaming at you with blood spraying through wounds on their throats. It's definitely more in the vein (so to speak) of classic Hammer horror than the Lovecraftian chills happening everywhere else in this late part of the game.
Taking a circuitous route through the castle that recalls the careful improvised rooftop passageways of Dark Souls's Anor Londo, the player can eventually meet the Queen of the "Vilebloods", as they're called, and figure out why they were officially summoned to Cainhurst. They just need to get past the strongest of the Executioners, who stayed behind to ensure the Vilebloods would never rise again...
Martyr Logarius is no joke. I might call him the most comparatively difficult boss in Bloodborne, though perhaps only because you can first encounter him at a stage of the game where you have very little hope of defeating him, such is the nature of some of these optional areas and when they first become available. He fights like a hunter NPC i.e. a CPU enemy who fights uncannily like a rival PvP human player, which makes him difficult and unpredictable enough, but he also has an array of nasty spells that involve skulls for whatever reason and is a lot taller than you to boot, which gives him the advantage of reach. You might not think it of a frozen old man, but he moves extremely fast and you can't take your eyes off him for a second.
I would liken this fight to Gwyn, the Lord of Cinder: the fight that concludes Dark Souls. Both opponents are elderly and haggard living corpses that are easy to underestimate. That's by design, of course: when Logarius is awoken from his slumber, he very deliberately stretches his hands and feet to restore feeling in them before slowly raising from his throne atop Castle Cainhurst and prepping his enormous scythe weapon. The player has to close the distance while avoiding the spells he flings out while standing perfectly still, adding to the illusion that he can barely move, and the player only discovers last-second that the old man is far more spry than he looks.
I'll admit to leaving this one to far later in the game - the summons to Cainhurst can be acquired as early as the Forbidden Woods, but it wasn't until after The One Reborn that I felt strong enough to defeat him. Like many battles with still-rational human beings, it's one that relies on strategy, speed and using the same tricks of the trade against them, because they have all the strengths you do and then some.
Upper Cathedral Ward
The Upper Cathedral Ward is another optional area that can be unlocked after moving through Yahar'Gul, and offers a glimpse into the highest tier of the Healing Church and how and why the clergy lost their way. It's not a big area: you move through a large chapel-like building and release the gates on the other side, wrapping back around to the start, but the enemies around here range from barely effective "celestial larvae" to much stronger versions of the werewolf beasts and Cleric Doctors that you previously met in the other Cathedral Ward areas. The concentration of high-level clerics up here has spawned far stronger monsters, but it's the larvae that are the most puzzling: by all accounts, the Church has been seeking the Great Ones through transfusion their blood. Why are there creatures that are closely related to Great Ones roaming around, if that's the case?
The most striking aspect of Upper Cathedral Ward, and an element that is fairly understated everywhere else, is its music. It's a very somber and slow lullaby tune that gives Upper Cathedral Ward a far more eerie tone, in part because very few enemies in this area make any noise to drown it out. It's not clear if the music is non-diegetic, but you can assume it isn't: none of the Souls games' sound design is by chance or (purely) for atmosphere outside of boss fights. They all have their sources, whether it's the singing noblewoman in the Tower of Latria or the melodic Demon of Song in the Shrine of Amana. Given that the highest rank of the Healing Church are referred to as the Choir - as evinced by the Choir set of clothing you can find in this area - you might assume the singing comes from them.
The Celestial Emissary is your Royal Rat Vanguard fight, in that you have a group of identical opponents that hides a creature that is actually the possessor of the boss health bar. The first half of the fight involves tracking the correct target down amidst his constantly respawning clones, making this fight the classic minion boss where you need to carve a path to the critical target. He's the only one not actively pursuing you, which makes him both easier to determine and more difficult to reach. In the second half of the battle, he grows to be much taller than his compatriots and fights just like them, but with the benefit of the added reach and damage. He's no longer concerned about hiding in plain sight, and the player needs to focus on evasion on top of continual damage.
The Celestial Emissaries are the first enemies you meet that are clearly touched by a Great One in some manner: they're humanoid, but have been transformed beyond human recognition into something definitely not beast-like. They almost look like alien grays, in fact, with large bulbous craniums and no visible mouths. There's plenty of odd little hints about what these guys are, but the standard explanation seems to be that they're humans that have been warped by the Great Ones directly (or through experimentation) rather than corrupted via blood and turned into beasts. Effectively, they are evolved forms of humans: the form that Byrgenwerth and the Healing Church have been pursuing all along. It's not completely clear if the transformed Celestial Emissaries in this battle are what remain of the Choir echelon of the Healing Church after the player empowered the Great Ones by breaking the veil between their reality and your own, but given the next boss it seems entirely likely.
Ebrietas, Daughter of the Cosmos
There's very little running around to separate the Celestial Emissary boss fight and the one that follows. Ebrietas is a trapped Great One: the secret that the Healing Church has been hiding and their greatest discovery when excavating the ruins beneath Yharnam. The Choir have been keeping Ebrietas secret, naturally enough, instead focusing on the Blood transfusions as a smokescreen to keep everyone - possibly including the Vicar Amelia, as well as numerous other clerics who became beasts - in the dark about the living, breathing Great One they have locked up in their basement.
Ebrietas is, like Rom, initially apathetic about your presence at her Altar of Despair. It's possible she regards all humans in the same disinterested manner, which probably allowed for her capture to the Choir's special chambers beneath the city. She'll retaliate only once you've raised weapons against her. Like the One Reborn, she is a massive and sluggish opponent that can easily be maneuvered around by the quick and nimble hunter, but she's got a nasty arsenal of abilities to rely on to compensate for this weakness. The one that is likely to kill you the first time you encounter it are her eye lasers, which will quickly combo and murder you if you aren't in the process of running away from it at an angle. She also has an aura that will hurt you if you're too close, dissuading the usual strategy for larger opponents where the player can get inside their attack radius and hacks them to pieces, and she'll also spit blood at you for a damaging attack that also causes the frenzy meter to fill up, which might well result in instant death if filled all the way.
Ebrietas's design is pure Lovecraft: a gooey white nonsensical combination of horns, limbs, wings and tentacles that's difficult to stare at. As we get closer to determining who and what the Great Ones are, Ebrietas helps to emphasize where their literary origins lie. It's less clear in the timeline when the Church first encountered Ebrietas, whether it was shortly before the night began or long before the player ever arrives, and how much she has contributed to their knowledge of the Great Ones, but it's evident from the many eldritch beings wandering around just outside in the Upper Cathedral Ward that she's almost certainly their source. The question remains, then: were these humans who asked to be "evolved" into Cthulhoid beasts by Ebrietas's power, or did Ebrietas press the issue when the blood moon rose and the Great Ones' time seemed nigh...?
Nightmare of Mensis
The Nightmare Frontier, and the passage through Yahar'Gul, both lead to this particular location: the dispossessed headquarters of the School of Mensis in the metaphysical realm of nightmare. Through this, the proper final dungeon of the game, the player uncovers the role the School of Mensis played in the coming of the Great Ones and puts an end to it once and for all. An exceptionally cleverly designed and dangerous area, it progresses ever vertically: it's possible to create a chain of elevators that leads directly from the bonfire at the base of the School to its very top, where the final boss (or one of them) awaits. Strap yourselves in, this is going to be a long one.
The most pertinent danger when entering the Nightmare of Mensis is a psychic force so powerful that it can damage and frenzy you just by being in its line of sight. You don't get to see what this source is until far later in the level: all you can see is an eerie orange glow from a room way higher up in the massive School of Mensis building. You might, however, make some educated guesses as to its true form from earlier examples of this sort of effect: there are certain enemies in the game, one or more of which may have been encountered in the Nightmare Frontier, which frenzies you (that is, briefly overpowers your senses and causes a huge amount of damage) if it does as much as glance in your direction. Oddly, they look like giant walking brains made of messengers - the little white goblin creatures that carry online correspondence and blood stains - and the body of the animated doll from the Hunter's Dream. Whether or not that has any bearing seems ambiguous: it could just be that your brain is compiling the creature's appearance out of familiar elements, because the real creature's shape is too inexplicable to contemplate - hence the frenzy. It's everyone's favorite aspect of Lovecraftian fiction: the idea that a creature so irrational in its composition that it would drive a rational person mad simply from knowing such a thing could exist, and feebly trying to process its appearance mentally and coming up short.
The Nightmare of Mensis also hosts little mannequin figures that won't hurt you unless you get too close, as well as various nightmare versions of creatures you've met already: the startling carrion crow enemies and the tenacious hounds of Central Yharnam, for example, only now with their heads switched around. The giant pigs of the Forbidden Woods are here too, only now they have a dozen eyes. There's shrouded figures that fight like the Shadows of Yharnam, only now without the snakes. And, of course, there's the enormous Mother Brain. I doubt that's its real name, but it's the source of the psychic long-distance attacks from before and is effectively a giant version of the aforementioned frenzy creatures. There's a method of dropping it down a giant pit and then finding a way down into the inky void below and finishing it off, which is oddly satisfying after the amount of trouble it puts you through in the first stage of the level.
As you continue to ascend, you'll meet this next boss along the way.
Micolash, Host of the Nightmare
Micolash is the head of the School of Mensis and perhaps the last human being alive inside the nightmare, aside from you. His is one of the more interesting fights in how the game actually uses the level design to confound and disorient you: he fights like a hunter, naturally, though the challenge is more in finding him and getting past the minions and traps he has scattered around the enormous library that sets the stage for this battle. The fight consists of two conflicts inside enclosed arenas, the first of which concludes with him escaping and the player in hot pursuit. It's easy to get turned around when running after him, and you need some idea about where to drop down through holes and when not to walk out into an obvious trap. After the second arena fight, he finally dies, despairing that he is "waking from the nightmare".
Micolash would make for an interesting interview with the amount of knowledge he has, if his being trapped in the nightmare for so long hadn't turned him completely insane. Whatever knowledge he garnered from marooning his entire School in a realm between realms died along with him, though he's not really the source of what had happened either; like Vicar Amelia he's simply another human victim of the Great Ones and their devices, though hardly blameless. As a combatant, he's fairly weak but for two Arcane-empowered hunter abilities, both of which can eventually be acquired by the player: the augur of Ebrietas, which allows players to reach across with a mass of tentacles for a very fast stun attack, and The Call Beyond which works like the homing soul arrows of previous Souls games. Neither should be taken lightly, even if Micolash doesn't have a whole lot of physical prowess to fall back on.
Mergo's Wet Nurse
It's never made entirely clear who or what Mergo is, only that it is the source of the nightmare and is guarded by this being, who resembles a tentacled monstrosity crossed with the Grim Reaper. Most lore would point to Mergo as being the infant product of a human mother and a Great One. Evidence of this comes from the various other suddenly pregnant female NPCs you encounter after the blood moon rises, each of which is bearing the child of a pure Great One, possibly as a convenient if disturbing means of physically manifesting in this world. Mergo can only be heard and not seen - the baby's crying, which is intensified in this fight - and disappears along with the nightmare dimension itself once the Wet Nurse has been slain. To that effect, the Wet Nurse is the only obstacle standing between you and the timely rescue of Yharnam from its eternal night of the hunt (should there be any people still left alive, that is).
The Wet Nurse fight has more in common with those against beasts than the Great Ones, oddly enough, in that most of its attacks involve large sweeping strikes with its multiple arms and scythe weapons. The idea is to get behind it to avoid most of its attacks, and strike whenever there's an opening in its relentless swipes. At one point in the battle, however, it turns the tables around and creates a distracting purple fog that greatly obscures your view of the arena. At the same time, it summons clones that briefly appear behind you, lunge forward to attack, and then vanishes again just as quickly. It's possible to focus attacks on the non-clone version of the boss during this time, who doesn't do much (you could assume that the illusion magic is taking up all her concentration), but it's safer to simply keep dodging around until the fog finally lifts some minute or so after it appears. It's a battle that encourages aggression: pick your moment and strike without hesitation, because the longer the fight continues the greater the chance for an ambush or fog event.
Once the Wet Nurse is destroyed, the usual "Prey Slaughtered" alert is replaced with a "Nightmare Slain" to indicate the end of a very long night. Mergo the infant whines his last and disappears forever, his attempts to breach our world thwarted at the last second and with it the invasion of the other Great Ones, if indeed that was their plan all along. You should be done, right? Well...
That's right. The peaceful and utility-rich hub of the game is also the location of its final conflict, depending on how you choose to see the game out. The ornery and forgetful caretaker of the Hunter's Dream, the retired hunter Gehrman, has been either dispensing advice the entire game about where to go next in the story or taking it easy snoozing in the garden. After Mergo's Wet Nurse, however, he moves to a previously closed off region of the Hunter's Dream beneath a large tree to await the player and discuss the dissolution of their association with the Hunter's Dream and its occupants. The hunter's task is over, and the long night has been quelled. Should the hunter submit their life, Gehrman rises from his wheelchair, pulls out a giant scythe and beheads the hunter. This act separates the link between the hunter and the dream, allowing them to wake up to a Yharnam seeing its first sunrise in possibly years. However, should the player refuse...
Gehrman, The First Hunter
The final hunter enemy of the game and, naturally enough, its most powerful. Gehrman is like passing from the qualifiers of EVO to meeting Daigo: other hunters might have impressed you with their skill, but Gehrman is the absolute master. He'll not only dodge and strike you like a hunter, but he'll also hit you with visceral attacks and the "dodge around to the back" evade roll with follow up, two difficult combat maneuvers the player is also capable of doing but only if they have the timing to pull it off. His weapon of choice, the Burial Blade, is one of the most damaging of all the weapons in the game, and he'll freely switch between its two-handed form and its one-handed plus firearm form to keep you guessing. Given that he's a final boss, he won't stop there either: he'll buff himself near the end of the fight with a form of arcane energy that makes him exceptionally hard to stagger and allows him to teleport around, adding to the level of danger he presents.
As with many of the game's boss fights, it's simply one hunter versus another, and it's up to the player to utilize all the tricks they've learned against the man who essentially invented them all. It's not an easy battle, in other words, and there's no obvious way to make it easier on yourself except to know the game's combat mechanics front and back and be hopeful that he doesn't wipe you out with a devastating combo.
Should Gehrman fall, the player is met with the true mastermind behind the endless night and the Hunter's Dream: an unnamed presence that floats down from the blood moon and embraces the player. This horrific violation transforms the player into the new custodian for the Hunter's Dream in Gehrman's place, ready to accept and acclimatize new hunters and keep the cycle going forever. Though if one were to swallow three special key items heavily implied to be necessary to evolve into a Great One before defeating Gehrman...
The true final boss of the game, at least outside of DLC. The Moon Presence is actually deceptively easy: he's meant to be the game's Nyarlathotep equivalent, which means he's more of a devious trickster entity who engages with humanity to screw with them rather than a powerful unknowable being like Cthulhu or Yog-Sothoth who would blink us out of existence if they cared enough. He clearly didn't expect a fracas when he floated down to acquire a new human mindslave to serve him for the next few centuries. He fights like a combination of a beast and a Great One: a four-legged creature that uses fast swipes and movements, but can also summon eldritch energies when the fancy strikes him.
He's not nearly as difficult as Mergo's Wet Nurse or Gehrman, and it's likely the player will have no difficulty slicing him to pieces. Rather than being an anticlimax, the fight feels like you've finally won against an elusive foe who would've otherwise kept this masquerade going forever. It's like somehow beating the devious Mantorok after Eternal Darkness ends, or confronting Izanami at the end of Persona 4: its through your own perspicacity and desire for truth that you were able to reveal the real perpetrator and bring them to justice.
After the battle concludes, the player is no more: what is left is the larva of a Great One-To-Be, implied to be the hunter's new form, who is taken away by the doll to be raised quietly in the Hunter's Dream that it might one day supplant the Moon Presence and become the next cosmic mastermind behind humanity's endless suffering. Perhaps the cycle wasn't broken after all. Still, you're now on the top of that particular totem pole of madness, so why worry?
That'll do it for both this edition of Bosswatch and for Bloodborne itself. I look forward to bringing this series back once I get my hands on Dark Souls III, but for now I think it's time to unwind with something simpler. Which is to say, something that won't inspire two 6000-word blogs in the same week. Oofa doofa.
Thanks for reading, all, and feel free to post in the comments any corrections or your own interpretations of the lore. People still like to talk about Bloodborne almost a year after its release, right?