Accursed Healer 

Prerequisites: The ability to cast spells that restore hit points
You can corrupt your healing spells with necrotic energy. You gain the following benefits:

• When you cast a spell that causes a creature to regain hit points, you can choose to cast an accursed version of that spell. The target of the spell must make a Constitution Saving throw against your spell save DC, taking nectrotic damage equal to the number rolled on the spell's dice on a failed save, or half as much on a successful one. The spell must involve a dice roll to be affected by this feat.

• When you cast a spell that causes a creature to regain hit points that cannot target or affect undead, it can target or affect undead. You may make this choice individually for each creature the spell targets.

• Your healing spells restore a number of additional hit points equal to your spellcasting ability modifier when used on undead.