Efficiant Magic

Transcendence

Recover used spell slots when casting. When you cast a spell using a spell slot of second level or higher, you can regain a used spell slot of a lower level.
When you use this ability, roll a hit die. You lose a number of hit points equal to your roll and your hit point maximum is lowered by the same amount. The number of dice you roll increases by 1 for every time this ability is used. Your hp max and number of dice rolled both reset when you finish a long rest.