Origin of the Hidden Ones

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.) I — This Saga deals 4 damage to any target. II — Create two 1/1 black Assassin creature tokens with menace. III — Whenever an Assassin you control attacks this turn, create a 1/1 black Assassin creature token with menace that's tapped and attacking.