Bloodletting

As an added cost to casting this spell, you take 2d6 necrotic damage which cannot be reduced or avoided in any way. On the turn you cast Bloodletting, you may cast any other spell you know that has a casting time of 1 action, regardless of whether that spell is a Cantrip.

The next necromancy spell you cast that deals damage deals an additional 4d6 necrotic damage to one damage roll of that spell. 

When you cast this spell using a spell slot of second level or higher, you take an additional 1d6 necrotic damage and deal an additional 2d6 necrotic damage for each spell level above first.