Yamato

Evocation Casting Time: 1 bonus action Range: Self Components: V, S Duration: Concentration, up to 1 minute You channel your focus into a single powerful strike. Your next melee weapon attack within the duration has advantage, and on a hit, it deals an additional 3d12 cold damage. If the attack reduces a creature to 0 hit points, you regain hit points equal to half the damage dealt. Your target have to roll a constitution saving throw to suffer only half damage.