Mistform

[Meglobob]

Soul slay does 999 damage, I think, you see the number pop up, when the unit dies in combat, so mistform could in theory protect you once.

Petrification is an MR check? So I doubt mistform helps at all.

Interesting idea with stone sword/mistform/ritual of returning, I hope it does work, as finding combos like that makes Dom3 great.