When A Killer Among Us enters the battlefield, create a 1/1 white Human creature token, a 1/1 blue Merfolk creature token, and a 1/1 red Goblin creature token. Then secretly choose Human, Merfolk, or Goblin. Sacrifice A Killer Among Us, Reveal the creature type you chose: If target attacking creature token is the chosen type, put three +1/+1 counters on it and it gains deathtouch (Any amount of damage this deals to a creature is enough to destroy it.) until end of turn.