King Arthur, the player character from the original, has succeeded in uniting the lands south of Bedegraine forest, resolving many of the mortal's issues with the enigmatic Sidhe council in the process. However, the lands to the north of the Bedegraine forest remain untamed and hostile, serving as a home and stronghold to entities such as Queen Morgawse: the Witch Queen of Orkney- an enemy who for the most part only managed a few indirect strikes at the player in the original.
King Arthur has good reason to directly fear the Witch Queen now, as she finally succeeds in finding and reawakening the ancient Fomorians- demonic entities who apparently existed not long before the gods came into existence. Fearing the worst, King Arthur arranges a meeting with Sir Kay, Sir Lancelot, and his wife Guinevere in order to determine what to do. They meet at a shrine to the holy grail, where a mysterious disaster occurs. The grail explodes, leaving absolutely no trace of Kay, Lancelot, and Guinevere. Only the barely-alive Arthur remains, as he is stricken with a grievous wound that refuses to heal.
King Arthur's predicament affects the entirety of his lands as the legends of the land suffering alongside their one true king are realized. As the whole land descends into chaos and decay, the knights of the round table are scattered; some being stricken by the chaos in some way, others departing to see if they can deal with matters on their own. Matters are only made worse when the Fomorians begin pressing southward, inflicting many with their enslaving curse.
From the stronghold that protects the sickly Arthur within the Bedegraine forest, players take the role of Arthur's son William, and are entrusted with the task of reuniting the round table, rebuilding the land, finding a way to heal Arthur, and defeating the Fomorians.
Just like the original King Arthur: the Role-Playing Wargame, King Arthur II is an RTS/RPG hybrid. The vast majority of gameplay elements from the original return, though they have been balanced to each other relatively differently.
In conjunction with the original's four season turn structure, the campaign map allows players to pursue text-based adventures, build structure upgrades, perform research, and move armies. Many of these features have been restructured in King Arthur II though. King Arthur II lacks an equivalent to the original's strongholds, instead spreading out structure upgrades among effectively every type of structure present in the provinces. These upgrades are also not global effects as often as they were in the original, instead only applying to the assigned liegelord of the province they are built in.
Research now requires 'lore points,' which are used to determine how far players can proceed along the now singular tech tree (Compared to the three seperate research trees the original had). Lore points can be gained through questing and certain structure upgrades.
Unlike the original, where Knights were individual characters that could be attached to any unit, the Knights in King Arthur II now come with their own retinue units and don't need to be attached to any unit. Each army can only have a maximum of three knights, but players are not allowed to divide armies at will like they could in the original. Instead, there are only three pre-defined knights in the game who can lead armies. Unused units and knights are kept in reserve to be drafted into your armies later.
The real-time combat in King Arthur II works much the same as it did in the original, with capture points spread throughout the maps. These capture points provide various bonuses and spells and can help keep your army's morale up- just like in the original. Unlike the original though, where morale was a single bar for the whole army, each unit has their own morale level in King Arthur II. It is still possible to win by depleting the enemy's morale entirely, but it must now be done on a unit-by-unit basis.
The new additions King Arthur II brings to the real-time combat are magic penetration and aerial units. Each army now has a global magic shield, the strength of which determines which spells will work and which ones will have a chance to simply fail completely. Many spells now have a magic penetration stat which gives you an idea on when they can ignore the spell shield. This generally only applies to offensive spells, with friendly buff spells not having to deal with the magic penetration mechanic.