Death Strike

As an action, you can expend a Death Knight rune to heal for 25% of the damage you took in the prior round per level of the rune consumed,  you make a melee weapon attack as part of this action. You gain temporary hit points equal to 10% of the damage dealt per rune level.

At higher levels: Regain 25% of the hit points you lost since your last turn per spell level, and gain temporary hit points of 10% of the damage you dealt in the attack, both rounded down.