Or, he was split into two people.
Yea, but those soul gems are really horcruxes for Mannimarco. He's just biding his time awaiting the duckie... I mean, undead, revolution.
:turtle:
Unless he was forceably separated from his divinity, which coalesced into the necromancer's moon. As a side effect of the massive amount of power, he still had the ability to appear as a living altmer. Or something like that.
In other words, Mannimarco is on Nirn, mortal (or at least semi-mortal), and more powerful than ever, while his divinity or godhood is supended in the air, just out of his reach. We can debate exactly how powerful mannimarco truly is when you meet in him game all day long. Truth is, depending on your character and what you have the difficulty slider set on, he can be tough or easy. GAME PLAY MECHANICS!!!! Want a true representation of how tough he actually is? Try going on the cave without having Traven's help. Then we'll see what's up.
You back yet? Turned you into a worm thrall, didn't he? Yep. Quit bragging, then. You didn't defeat him on your other game. Traven did. You just couldn't see it because you were too busy taking credit for what the previous archmage just did.
j/k