Szarel, Genesis Shepherd + Cauldron of Souls + Clock of Omens + Yahenni, Undying Partisan

Szarel, Genesis Shepherd

Cauldron of Souls

Clock of Omens

Yahenni, Undying Partisan

How it works

1. Activate Cauldron of Souls by tapping it, giving two nontoken artifact creatures persist until end of turn.
2. Activate Clock of Omens by tapping the nontoken artifact creatures, untapping Cauldron of Souls.
3. Activate Yahenni by sacrificing one of the nontoken artifact creatures that doesn't have a -1/-1 counter on it.
4. When the creature dies, its persist ability and Szarel triggers.
5. Resolve the persist trigger, returning the creature from your graveyard to the battlefield.
6. Resolve the Szarel trigger, putting a number of +1/+1 counters on the other artifact creature.
7. Resolve the Yahenni ability.
8. Repeat from step 3 once, instead sacrificing the creature who had counters placed on it in step 6.
9. Repeat from step 1.

This fascinating loop turns a pair of artifact creatures into an endless cycle of sacrifice and rebirth, fueled by Cauldron of Souls granting persist to your creatures and Clock of Omens untapping that Cauldron by tapping those very same artifacts. As you sacrifice those creatures to Yahenni, Undying Partisan, Szarel, Genesis Shepherd steps in to distribute fresh +1/+1 counters that instantly neutralize the -1/-1 counters left behind by persist. This clever interplay ensures that neither creature stays dead for long, letting you churn out infinite artifact and creature sacrifices, enter-the-battlefield triggers, and death triggers at will.