Okay, here we go.
First red flag in my head was I remembered one of the dev team, possibly Schilling, saying there were dragons in the game. I was level 40, and almost at the end of the last story quest, and hadn't seen one.
So yeah, that confirms what the final boss is: a dragon. The only one I'm aware of in the game, despite the promise of dragons. Now, I don't need dragons in my game, but if you say there are dragons, put them in there. I'm sure, however, that now that Skyrim did it, every RPG is going to have to.
So yeah, you face a dragon. And it's similar to the Balor fight, in that it's more like a God of War fight than the other bosses. I suppose that's necessary. With KOALA's camera, looking up might be the hardest part of the challenge otherwise.
While I appeared to take a little health off him otherwise, there is only ONE way to really harm him (her, I think, but I can't remember) and I'm going to double spoiler that:
you need to build up your fate bar, Reckoning, and whale on him
It didn't take too long to figure this out, all things considered, and it's pretty easy to do. I tanked the boss as a mage with no potions. It's pretty damn easy to cheese him. Especially since that's pretty much what they require of you.