"Necropolis" - changes to creatures of levels 6-7.

What's the point of weakening them so much? It will result in the same thing – dead units, but not with a death blow, but with the presence of the unit on the battlefield. 20 defense and 120 hit points – just like a level 6 unit. They will still die in one hit, with a 50% chance.
Look at Ghosts, they are incorporeal, but their stats are no worse than other units.