Blightbeetle + Ashnod's Altar + Harmless Offering

Blightbeetle

Ashnod's Altar

Harmless Offering

How it works

1. Donate Blightbeetle to an opponent
2. Activate Ashnod's Altar 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. Repeat from step 2.

This clever loop weaponizes an opponent's own board against them by using Harmless Offering to gift Blightbeetle to the other side of the table. Once installed on your opponent's board, Blightbeetle's static ability completely shuts down the defining restriction of the undying mechanic—which normally prevents an undying creature from looping infinitely by slapping a +1/+1 counter on it upon revival. With that safety measure nullified, you can repeatedly feed your undying creature to Ashnod's Altar to generate an endless stream of colorless mana alongside infinite death, sacrifice, and entry triggers.