Cauldron of Souls + Dross Scorpion + Arsenal Thresher + Thermopod

Cauldron of Souls

Dross Scorpion

Arsenal Thresher

Thermopod

How it works

1. Activate Cauldron of Souls by tapping it, giving Arsenal Thresher persist until end of turn.
2. Activate Thermopod's second ability by sacrificing Arsenal Thresher, adding .
3. When Arsenal Thresher dies, its persist ability and Dross Scorpion trigger.
4. Resolve the Dross Scorpion trigger, untapping Cauldron of Souls.
5. Resolve the Arsenal Thresher trigger, returning it from your graveyard to the battlefield with a -1/-1 counter on it, and then choosing to reveal at least one artifact card from your hand to remove the -1/-1 counter.
6. Repeat.

This ingenious loop centers around Cauldron of Souls, which grants persist to Arsenal Thresher so that it can be sacrificed to Thermopod for red mana. Whenever Arsenal Thresher dies, Dross Scorpion triggers off the death of an artifact creature to untap Cauldron of Souls, resetting your engine. Meanwhile, Arsenal Thresher's own entry ability allows you to reveal artifact cards from your hand to place a +1/+1 counter on it as it returns via persist, instantly wiping away its newly acquired -1/-1 counter and keeping the loop ready to repeat infinitely.