Szarel, Genesis Shepherd + Cauldron of Souls + Clock of Omens + Krark-Clan Ironworks

Szarel, Genesis Shepherd

Cauldron of Souls

Clock of Omens

Krark-Clan Ironworks

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 Krark-Clan Ironworks 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 turns the flexible artifact-sacrifice outlet Krark-Clan Ironworks into a boundless fountain of colorless mana by looping creatures through the graveyard and right back onto the battlefield. Cauldron of Souls plays a vital supporting role by granting persist to your creatures, allowing them to cheat death the first time they fall, while Clock of Omens keeps the Cauldron active by tapping those creatures for an untap. Meanwhile, Szarel, Genesis Shepherd ties the whole mechanical web together by converting each sacrifice into a stream of +1/+1 counters—which conveniently cancel out the persist mechanic's -1/-1 counters, resetting the creatures so the loop can run indefinitely.