actually i went through it recently, like a week back, and i took nebulus. took me a few tries, i was trying to do it without using up potions. i actually got it on my first try using everything but 2(of 4) xs potions.
the bone attack from the bird i.d., the shield(and health combined with the item that makes them lose health instead of you) from the battle i.d. and any healing from a fairy i.d. help. of course i did this just before draculas castle.
i had made the feather sword, which is the strongest sword in the game, and i used that over the warhammer because it's faster. when you drop him to half health you can really wail on him while he's pulling that corpse out of the ground just before he grows huge. at that point when he's gigantic, put on your best fist weapon double jump and assault his knees. eventually he goes back to normal size, but by then he shouldn't have much left and you should know what you need to do to finish it off. my only regret is i never made the steal.