Cauldron of Souls + Dross Scorpion + Ashnod's Altar + Encroaching Mycosynth

Cauldron of Souls

Dross Scorpion

Ashnod's Altar

Encroaching Mycosynth

How it works

1. Activate Cauldron of Souls by tapping it, giving the creature with bloodthirst persist until end of turn.
2. Activate Ashnod's Altar by sacrificing the creature with bloodthirst, adding CC.
3. When the creature dies, its persist ability and Dross Scorpion trigger.
4. Resolve the persist trigger, returning the creature from your graveyard to the battlefield, which enters the battlefield with at least one +1/+1 counter on it due to its bloodthirst ability.
5. Resolve the Dross Scorpion trigger, untapping Cauldron of Souls.
6. Repeat.

This ingenious loop relies on turning your entire board into a machine of perpetual motion, beginning with Encroaching Mycosynth which ensures every nonland permanent you control is an artifact in addition to its other types. With that blanket transformation in place, Cauldron of Souls can target any creature and grant it persist, allowing it to return from the dead with a -1/-1 counter whenever it perishes. When you sacrifice that creature to Ashnod's Altar, you not only harvest a tidy sum of colorless mana, but you also trigger Dross Scorpion—which, thanks to your Mycosynth, easily untaps the weary Cauldron of Souls so the cycle can begin anew. Because the creature returns with its persist trigger satisfied by its previous death, and its counters continually reset, you can repeat this sacrifice-and-return dance indefinitely to fuel your victory.