You learn to exploit the potency of your blood to aid your allies.

Whenever you cast a spell that restores hit points, you can choose to take damage equal to your cleric level to roll the healing twice, and take the higher result. This damage cannot be reduced by any source. Furthermore, when you cast a spell that restores health to one or more allies, those allies gain a bonus to their next attack roll equal to your spellcasting ability modifier.

However, your wounds don’t close easily. Whenever you take damage from any source, you cannot regain hit points until the end of your next turn. 

“Your pain echoes through your bones. You ease their wounds with trembling hands.”