Hellmaker

-You gain resistance to one damage type of your choosing from the following list: Acid, Fire, Lightning, or Necrotic.

-You learn the Hellish Rebuke spell as a first level spell and can use it a number of times per long rest equal to your proficiency modifier without consuming a spell slot. The damage type of this Hellish Rebuke is converted to the damage type chosen to be resisted to (ie, Acid resistance means Acid damage from Hellish Rebuke)

-If you get hit by a critical attack and use this feature: the creature that landed the attack cannot make the save to take half damage, they lose any resistance to this features damage type until the start of their next turn, and the damage is 20 instead of 2d10.