Blightbeetle + Altar of Dementia + Bazaar Trader

Blightbeetle

Altar of Dementia

Bazaar Trader

How it works

1. Donate Blightbeetle to an opponent
2. Activate Altar of Dementia 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 Altar of Dementia ability.
5. Repeat from step 2.

This crafty little loop relies on feeding an undying creature to Altar of Dementia over and over, turning a sacrificial engine into a game-ending mill machine. The magic happens because Blightbeetle's passive static ability stops your opponents' creatures from ever receiving +1/+1 counters—so when you use Bazaar Trader to hand that very same Blightbeetle over to an opponent, their side of the board becomes a harsh anti-counter zone. As a result, your sacrificing creature's undying return triggers continuously bypass their usual drawback, letting you sacrifice, resurrect, and mill your target player infinitely without ever fizzling out.