Even though all of those are correct none of them are helpful, because Mundo does not cast spells, Except maybe fire shield. Nor Fly. Nor is he undead. And he is absolutely not smart.
Also, by "most things" I didn't mean stuff like damage, I meant like slowing, stunning, paralyzing, or at least he is extremely resistant. Should have clarified.
Truenaming is a promising source of plentiful regeneration, or it would be, if it weren't impossible. I'm looking for the ability to gain a burst of fast healing at no action cost.
I want to basically retain maximum effectiveness all day while being able to do all these things. If it's impossible to do this without tome of battle, just say so now.