Szarel, Genesis Shepherd + Cauldron of Souls + Clock of Omens + Phyrexian Altar

Szarel, Genesis Shepherd

Cauldron of Souls

Clock of Omens

Phyrexian Altar

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 Phyrexian Altar 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. Repeat from step 3 once, instead sacrificing the creature who had counters placed on it in step 6.
8. Repeat from step 1.

This intricate engine harnesses the mechanical synergy between Cauldron of Souls and Clock of Omens to repeatedly cycle artifacts through the graveyard, all while Phyrexian Altar converts those sacrifices into a limitless supply of colored mana. As each creature falls and returns via its newly-granted persist ability, Szarel, Genesis Shepherd turns those sacrifices into scaling power boosts by piling +1/+1 counters back and forth between your creatures to cancel out their -1/-1 counters. Because Szarel, Genesis Shepherd also lets you play lands directly from your graveyard, this setup not only fuels an endless stream of artifact death, entry, and leave-the-battlefield triggers, but also provides the resilient framework needed to sustain a massive board state.