Oh the dungeon with the necros and skeletons. If it helps anyone my setup was Bound Bow, Sneak and Throw Voice. It really makes things less hectic. As for Malyn, I'm thinking I'll need to level up once more because I can get a perk that banishes stuff with the Bound Bow, but I need one more point to unlock it.
That should work well then, all Malyn servants are Dremora. It'll be just you and him if all goes well.
One thing though that I'm not certain of. Malyn says to you when entering his realm that the place is pretty much his own little slice of Oblivion. Therefore, it's possible that the inside of Azura's Star IS the homeplane of the Dremora. That would mean Banishment might not be possible. This is a far off possibility though, I very much doubt that they bothered to cover such a small possibility and I'm uncertain as to how they term Banishment and it's uses. What I'm describing is sort of a D&D interpretation of the fact that when traveling to other planes, banishment of native beings doesn't work because its you that is the extraplanar invader.
Again, what I described is very far off and not likely