Echoing Wrath

You gain 1d4 temporary hit points, which last until the end of your next turn.  If you take damage that causes you to lose these temporary hit points, an amount of damage equal to the number of temporary hit points lost is reflected back at the attacker.  This damage ignores resistance and vulnerability.   

The amount of temporary hit points you gain increases by 1d4 when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4).