Channel Divinity: Atonement

As an action,  you present your holy symbol and speak a prayer to destroy another creature’s life force. When you hit a creature with a spell attack, you expend your Borrowed Divinity to mark a target for a full round of combat. You focus your divine energy to deepen every wound the target would take. The damage is necrotic and equals 5 + twice your cleric level.

Divine Empathy: Using your divine magic this way requires you offer a portion of your own health every time bonus damage is dealt. When the marked target takes damage, you must make a Wisdom save against your own spell save DC or take half of the bonus damage dealt rounded up. On a successful save, you take a quarter of that damage rounded up.