Blightbeetle + Carrion Feeder + Bazaar Trader

Blightbeetle

Carrion Feeder

Bazaar Trader

How it works

1. Donate Blightbeetle to an opponent
2. Activate Carrion Feeder by sacrificing the undying creature.
3. When the undying creature dies, its undying ability triggers, returning itself from your graveyard to the battlefield without a +1/+1 counter on it due to Blightbeetle.
4. Resolve the Carrion Feeder ability.
5. Repeat from step 2.

This loop leverages Blightbeetle's passive static ability to rewrite the rules of combat and counters, ensuring that any creature returning with undying sneaks back in clean of +1/+1 counters because your opponents' creatures can't have them placed. To get this engine running under your control while the beetle actually shuts down your opponent, Bazaar Trader plays the crucial matching piece by permanently gifting Blightbeetle across the table. Once it resides safely on the other side, you can repeatedly feed creatures to Carrion Feeder to fuel an infinite loop of sacrifices, leaves-the-battlefield, and death triggers.