Vitality Spellcaster
General Feat (Prerequisite: Level 4+, Spellcasting ability 17+)
You have learned to channel your own physical essence into pure magical energy, allowing you to cast powerful spells beyond your normal limits at a devastating cost to your well-being.
You gain the following benefits.
Ability Score Increase. Increase your Intelligence, Wisdom, Charisma, or Constitution score by 1, to a maximum of 20.
Essence Casting. When you wish to cast a spell you prepared for which you have no available spell slots, you can attempt to cast the spell anyway.
Make an Intelligence (Arcana), Wisdom (Religion), or Wisdom (Nature) check against a DC equal to 10 plus twice the spell level.
On a success, you cast the spell normally without requiring a spell slot.
On a failure, your spell fizzles to no effect.
Additionally, make a Constitution saving throw against a DC equal to 12 plus twice the spell level attempted.
On a success by 5 or more, you gain a number of levels of Exhaustion equal to half the spell level (rounded up), minus one level.
On a success, you gain a number of levels of Exhaustion equal to half the spell level (rounded up).
On a failure, you gain a number of levels of Exhaustion equal to the spell's level.
On a failure by 5 or more, you gain a number of levels of Exhaustion equal to the spell's level, and if you survive, you fall into a comatose state for 1d4 hours.