Blightbeetle + Switcheroo + Yahenni, Undying Partisan

Blightbeetle

Switcheroo

Yahenni, Undying Partisan

How it works

1. Donate Blightbeetle to an opponent
2. Activate Yahenni 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 Yahenni ability.
5. Repeat from step 2.

This clever loop relies on a brilliant rules interaction between a donated Blightbeetle and your own undying creatures, ensuring that whenever a sacrificed creature returns, its usual +1/+1 counter is completely prevented from being placed. With that prevention in place, Yahenni, Undying Partisan acts as the ultimate sacrifice outlet and payoff, growing larger while keeping your other threats safe through its own activated ability. To set the entire engine in motion, you simply use Switcheroo to hand the Blightbeetle directly to an opponent, locking down their board's counter generation while opening the door to an endless cycle of sacrifices, deaths, and triggers.