Damnation

The caster sings a verse from the Book of Vile Darkness, draining all life force around the caster in a 20 foot radius. All creatures within the area of affect must succeed on a constitution saving throw or take 8d6 necrotic damage, taking half damage on a successful save. Undead creatures within the area of affect are healed by this amount instead. Additionally, if a creature dies from the damage of this spell - whether or not the constitution save was successful - that creature reanimates as a ghoul 1d4 turns later. The ghouls will attack whatever living creatures are nearby, and will hunt the living if none are found. 

 For each spell level this spell is cast above 6th level, the necrotic damage increases by 1d6.