Szarel, Genesis Shepherd + Cauldron of Souls + Clock of Omens + Grinding Station

Szarel, Genesis Shepherd

Cauldron of Souls

Clock of Omens

Grinding Station

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 Grinding Station by tapping it and 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. When the creature enters, Grinding Station triggers, untapping Grinding Station.
7. Resolve the Szarel trigger, putting a number of +1/+1 counters on the other artifact creature.
8. Resolve the Grinding Station ability from step 3.
9. Repeat from step 3 once, instead sacrificing the creature who had counters placed on it in step 6.
10. Repeat from step 1.

This loop uses Cauldron of Souls to grant persist to a pair of artifact creatures, allowing them to repeatedly return from the graveyard after being fed to Grinding Station. While Grinding Station's own ability triggers to untap itself whenever an artifact enters, Clock of Omens works alongside it by utilizing the creatures' taps and untaps to reset your resources. Meanwhile, Szarel, Genesis Shepherd turns every sacrifice into a distribution of +1/+1 counters that wipe away incoming -1/-1 counters, keeping the cycle going indefinitely and milling out your opponents.