Cauldron of Souls + Dross Scorpion + Arsenal Thresher + Ashnod's Altar

Cauldron of Souls

Dross Scorpion

Arsenal Thresher

Ashnod's Altar

How it works

1. Activate Cauldron of Souls by tapping it, giving Arsenal Thresher persist until end of turn.
2. Activate Ashnod's Altar by sacrificing Arsenal Thresher, adding CC.
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 engine uses Ashnod's Altar as the sacrificial engine to generate an infinite loop, turning your creatures into a river of colorless mana and death triggers. Cauldron of Souls plays a crucial role by granting persist, allowing your creatures to crawl back from the graveyard, while Dross Scorpion stands ready to untap your tools every time an artifact creature bites the dust. Finally, Arsenal Thresher acts as the recursive centerpiece; as it enters the battlefield, you can reveal artifacts from your hand to place a +1/+1 counter on it, neutralizing the persist -1/-1 counter so the loop can be repeated indefinitely.