Could have a few options here ....
Option 1, Bad Guy is clear Faction Leader of a particular faction from the beginning. If the Wii game could take any inspiration, he could start as Faction leader of the Ottomans, invading a dying Byzantium, or w/e. But that is largely boring, but would be the default 'fall back' choice.
Much more interesting is if he is a Mercenary on a quest of his own, embroiling all of Europe in a war. He would travel from Spain, to Germany, to Russia, to England, to Greece, and even to the deserts beyond North Africa, in the search for 'Shards' of his Weapon.
In such a game, the villain would be a perfect FOIL to the main character, and a true free agent, with much more complex AI than the typical 'lords'. He would be on a quest for various shards hidden throughout the game to empower his weapon 'Soul Edge.' Meanwhile, Main Character would probably start with 'Soul Caliber' ... or, maybe, would start with a different magical weapon (perhaps you pick which one u want at Character creation?). It levels up over time, as you kill more enemies (specifically), and at high levels the weapon has access to some of the darker abilities available to Soul Edge. You could probably level up the weapon like you would a Companion ... only instead of increasing Stats+Skills ... you increase Weapon Stats and Magical Skills (spells get stronger, buy new spells, increase speed/etc). Could have a "siege mode" where the weapon gets shorter, with possible perks including Bonus vs Shields *and* Penetrating blocks, but without the capability of most (if not all) of its spells, and certainly none of the 'area effect' ones. One such spell (that is usable in siege mode, as well as standard mode) would be Forcefield, which would be a temporary Field of Plasma that catches arrows fired onto the MC and places them into his quiver (or into his inventory if no quiver equipped ... or into the Victory Loot pile, if Inventory is full). The graphic could be for any arrows to be 'stuck' in the area around the main character (radius of 2.5 feet from character model). And maybe a slight shimmer effect (which doesn't effect vision when holding 'shift'). Or a 'chain lightning' that bounces from body to body (friend and foe alike) to those within half a foot from each other. Temporarily stunning all effected (with 15% chance to knock them to the ground) and dealing a minor damage of 2-10 hp, depending on factors ... (10 for first hit, 6 for all secondaries, and 2 for any after that).
Fireball is fairly self explanatory, but 'Soul Wave' would be a Gravity Well type of spell which pulls/drags living bodies towards the user, and also slowly draining the life from those effected. Would have a wide area of effect, and, depending on the distance, would drain a different amount of life. Say, those immediately on the MC would be drained 5 hp per second, while those at the farthest distance possible would be effected at 0.5 hp per second (or 1 hp per second). The Downside is that this also drains the HP of the Caster, thus making it impossible to maintain indefinitely. (alternatively, if a Magic Bar were added, could drain magic bar instead, or ... could drain both). Most spells should probably just have very limited shots per battle, similar to the way you have only 5 Throwing Axes, for instance. In this case though, the throwing axe is on fire, can travel twice as far, and explodes upon impact (fireball). The only real limitation is what can be added visually (and mechanically) to the game ...
Another interesting concept would be a 'Vampire Stilleto' which is like, a Knife or Dagger (no real range, decent speed, can't block) ... which, well ... successful hits "heal" user HP .... but the downside is that, unless its a REALLY weak opponent, its almost impossible to really use it well.