Cayth, Famed Mechanist + Yahenni, Undying Partisan

Cayth, Famed Mechanist

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing the persist creature.
2. When the persist creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When the persist creature enters the battlefield, its fabricate ability triggers, putting a +1/+1 counter on it.
4. Resolve the Yahenni ability, giving it indestructible until end of turn.
5. Repeat.

This clever loop relies on Yahenni, Undying Partisan's ability to sacrifice a creature at will to protect itself with temporary indestructible. By feeding a creature with persist into Yahenni's sacrifice outlet, you trigger its return to the battlefield with a -1/-1 counter. This is where Cayth, Famed Mechanist comes in: Cayth grants fabricate 1 to your other nontoken creatures, allowing that returning creature to immediately trigger its new ability and place a +1/+1 counter upon itself. Because +1/+1 and -1/-1 counters annihilate each other as a state-based action, the creature's slate is wiped clean of counters every single iteration, ready to be sacrificed to Yahenni all over again.