Blood for Blood

You burn your own life force to fuel incredible power, gaining the following benefit:

When you make a weapon attack, unarmed strike, or cast a spell that deals damage, you can choose to add your proficiency bonus to the damage roll.  However, the energy you infuse into your attack or spell comes at a cost. When you use this feature, you take damage equal to your proficiency bonus. This damage is the same type as the attack or spell you enhanced, bypassing resistances and immunities. This damage cannot be reduced or prevented in any way. Your hit point maximum is reduced by the damage taken every time. This reduction remains until you finish a Long Rest, or until you are affected by a Greater Restoration spell cast at 8th level or higher, the Wish spell, or Divine Intervention.