Blood for Power

You take 10 necrotic damage that can’t be reduced in any way. In exchange, you regain two 1st level spell slots. If you are immune to necrotic damage when you cast this spell, the spell fails.

At higher levels: When you cast this spell with a 2nd spell slot or higher, the damage you take increases by 10 for each slot above the first and you regain two spell slots of the same level you used to cast this spell.