Stalwart Successor + Puppeteer Clique + Umbral Collar Zealot

Stalwart Successor

Puppeteer Clique

Umbral Collar Zealot

How it works

1. Activate Umbral Collar Zealot by sacrificing Puppeteer Clique
2. When Puppeteer Clique dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Puppeteer Clique enters, it and Stalwart Successor trigger.
4. Resolve the Puppeteer Clique trigger, putting a creature from an opponent's graveyard onto the battlefield under your control.
5. Resolve the Stalwart Successor trigger, putting a +1/+1 counter on Puppeteer Clique
6. Resolve the Umbral Collar Zealot ability.
7. Repeat.

This clever loop turns graveyard thievery into an infinite engine by continually cleansing away the burden of death. Every time Umbral Collar Zealot sacrifices Puppeteer Clique, the Clique's persist ability brings it back bearing a -1/-1 counter, but Stalwart Successor immediately answers that setback by triggering to place a +1/+1 counter on it. Because the -1/-1 and +1/+1 counters annihilate each other as a state-based action, Puppeteer Clique is left pristine and ready to die again—while its recurring entrance triggers its own ability over and over to steal every single creature from your opponents' graveyards.