Equilibrium

By sacrificing your very life force you can convert it into magic. You lose 10 hit points which cannot be negated in any way when you begin to cast this spell. Once the spell has been successfully cast, you regain one expended 1st-level spell slot. If you do not have an expended spell slot available or do not finish casting the spell, the spell fails and the hit points are lost.

When you begin to cast this spell, you can choose to expend additional hit points, each additional 10 hit points expended increasing the level of the spell slot restored by one level.