Cataclysm

 After sacrificing ones life force, summon demonic energy and aim it at your target at risk to yourself. Roll a d100. 50+ causes equal to roll damage. 49-40 half rolled damage. 39-30 no damage done, skip rest of turn. 29-20 damage targets your nearest ally. 19-10 damage is turned on the caster. 9-1 roll a d20 and relieve the damage rolled and skip remainder of turn. Ability can only be used once per long rest.