Cauldron of Souls + Dross Scorpion + Mycosynth Lattice + Phantom Train

Cauldron of Souls

Dross Scorpion

Mycosynth Lattice

Phantom Train

How it works

1. Activate Cauldron of Souls by tapping it, giving the creature with bloodthirst persist until end of turn.
2. Activate Phantom Train by sacrificing the creature with bloodthirst.
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. Resolve the Phantom Train ability
7. Repeat.

This delightfully twisted engine relies on Mycosynth Lattice to turn the battlefield completely metallic, ensuring that Dross Scorpion can watch over every single death and untap Cauldron of Souls whenever an artifact perishes. By feeding a creature into Phantom Train, you trigger both its transformation and its demise, which instantly sets off Cauldron of Souls' granted persist ability to bring it right back. Because the creature returns with a -1/-1 counter while its entry is sweetened by a +1/+1 counter (such as from its bloodthirst ability), the two counters lovingly annihilate each other, leaving the creature completely clean and ready to be sacrificed all over again in an endless loop of mechanical resurrection.