Katsui Ryoku, Angel of Life

Partner with Bosi Suru, Angel of Death (When this creature enters the battlefield, target player may put Bosi Suru, Angel of Death into their hand from their library, then shuffle.)
Flying, lifelink, vigilance, retribution
Insular - When Katsui Ryoku, Angel of Life enters the battlefield, if you spent only white mana to cast it, Whenever a +1/+1 counter is put on this creature, restore 2.