Szarel, Genesis Shepherd + Cauldron of Souls + Clock of Omens + Woe Strider

Szarel, Genesis Shepherd

Cauldron of Souls

Clock of Omens

Woe Strider

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 Woe Strider 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 Woe Strider 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 intricate engine relies on a clever synergy of recursion and artifact manipulation to generate infinite loops. By granting persist to your artifact creatures via Cauldron of Souls, you can sacrifice them to Woe Strider to trigger their return; meanwhile, Clock of Omens taps those same creatures to untap the Cauldron, keeping the loop self-sustaining. Szarel, Genesis Shepherd ties the whole mechanism together by turning those sacrifices into a growing pile of +1/+1 counters to continually offset the persist penalty and pump your board.