Bethesda struck a certain tone with the numerous piecemeal add-ons to its recent Fallout games. Those bite-size wasteland episodes created relatively short, focused storylines that took place in discrete new environments and often compartmentalized the best facets of the core game, like exploration and player choice, that made it special to begin with. In stark contrast, Dawnguard, the first downloadable add-on for Skyrim, is more substantive and satisfying in structure and feel than any of the Fallout content. Where those add-ons were generally confined to a single new area with little or no connection to the game's original space, Dawnguard instead exists all over, inside, and around the land of Skyrim, not just adding a lengthy and well made central quest line but also sprinkling little morsels of major and minor new content into many a nook and cranny as well.
Vampires rule the central conflict of Dawnguard, as an ancient sect of especially powerful bloodsuckers has recently come back to prominence in the north of Skyrim and begun plotting to blot out the sun for all eternity. (Tamriel's vampires never have too much trouble with sunlight to begin with, but don't let that detract from the ominous threat of a neverending night.) Just a few minutes after loading a save with Dawnguard installed, you'll be approached by a courier or attacked by a roving pack of vampires, either of which informs you that the Dawnguard, the legendary league of vampire-hunters, has been reformed to fight the menace. You'll immediately head to the group's base to join up with them, and then set out to investigate the vampire lords causing all this trouble.
Dawnguard really caught my attention early on by giving me the chance to turn my back on the Dawnguard in the course of that first mission and join up with the vampires instead. While your choice of faction affects which set of quests you'll do early in the add-on's storyline, the majority of Dawnguard's plot and locations are pretty much the same either way. But who you side up with certainly affects the tone of your interactions with all the new characters, and there's a whole mess of unique side quests that go along with each faction. It's a nice, dynamic way to give you some control over the way things play out in your story, especially since it gives you a chance to take actions that sensibly correspond to the sort of good or evil character you've already played for dozens of hours in Skyrim.
The add-on also does a great job of conforming to the state of your particular game world. I noticed several instances of characters unique to this DLC referencing what I'd done in Skyrim's main storyline, and commenting on the nature of the civil war as I'd left it in my playthrough. Some existing locations are also altered to go along with the vampires' activities. You need to be level 10 before you'll start seeing the ambient events that invite you to start the DLC content, but you'd want to be at least that high just to have developed some powers and skills to use in the new quests anyway. On the whole, Dawnguard feels well integrated with all the existing content in Skyrim, in such a way that you rarely see the seams between the two releases.
Whichever faction you choose, you'll get the chance to become a vampire lord, a new kind of super vampire that morphs you into a third-person wrecking machine similar to the existing werewolf form. The vampire lord is good for some laughs, since it has several physics-based powers that let you sling enemies around like ragdolls, and it also comes with some extremely useful powers like a teleport and enhanced night vision. But moving around in an oversized third-person creature form hasn't gotten anymore elegant than it was before--there are plenty of interior areas you can't even fit through as a vampire lord--and it takes a long time to morph into and out of, so I ended up not using the full creature form very much. (Luckily some of the ancillary powers like the night vision work in your regular form.) There's an entire perk tree devoted to expanding your vampiric powers (and another one for werewolves, if you happen to still be one of those), so if you do go in for the creature action, there's a good deal of customization to tailor your hijinks with. And it's a simple affair to cure your vampirism later if you want to try it out and then go back.
The Dawnguard quest line is anchored by the add-on's new follower Serana, a good-natured vampire daughter who struck me as one of the more fleshed-out and sympathetic characters in the whole of Skyrim. Maybe it's natural that you'd feel more attached to a character who you spend a good 10 hours with, but Serana's embroiled in some good old-fashioned family drama and delivers enough well-acted voiceover that you end up feeling pretty bad about what she's going through. (It's worth noting that you're required to keep Serana as a follower for most of the storyline, in case you just hate using followers for some reason.) The Dawnguard quest line takes you to some pretty cool new areas, including a plane of Oblivion, a decrepit old castle with some nifty environmental puzzles, and a vast frozen valley forgotten by time. I found the quest in that valley to be sort of poorly laid out, which makes it drag on longer than it should, but otherwise the quests move briskly, and the whole thing culminates in a dramatic and explosive confrontation that's flashier than most of the stuff you saw in Skyrim itself.
One of the best things about the Dawnguard package to me is that it makes a bunch of big and little additions to the game even after you've dealt with the vampires. You'll come out of the main quest line with a couple of crazy items, like a bow you can shoot straight into the sun to rain hellfire down on enemies, and there's a good number of other unique items that you can uncover through side quests. (A headpiece that lets you have two standing stone effects at once, anyone?) There's at least one lengthy side quest in a unique dungeon and with an associated achievement and reward items that I'm aware of, as well as new types of armor, a new tier of "legendary" ambient dragon to fight, and some new spells and shouts to learn. Heck, I ended up with the ability to summon a spectral steed out of thin air, which is pretty great since I found managing live horses to be cumbersome in the original game. Again, this stuff is spread around the world in a way that keeps this add-on from feeling too self-contained.
Dawnguard offers far more than a self-contained episode in the Fallout vein--which it should, at double the price--but it falls just short of the scope of a traditional, pre-Internet boxed expansion pack. Still, it's a fine way to expand the already immense content offering of Skyrim, especially if you're still actively traipsing around those snowy hills in search of more adventure. If Bethesda can figure out a way to combine this style of across-the-board enhancement with a more substantial new landmass in the next inevitable Skyrim add-on, it'll really have created something special. This is already a good start.