Blightbeetle + Phyrexian Altar + Donate

Blightbeetle

Phyrexian Altar

Donate

How it works

1. Donate Blightbeetle to an opponent
2. Activate Phyrexian 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 revolves around denying your opponents the very mechanic that keeps Undying in check. By using Donate to hand over Blightbeetle to your opponent, its passive ability ensures that no creature they control can ever receive +1/+1 counters. With that restriction locked in place across the table, you can continuously feed an Undying creature into Phyrexian Altar; whenever it dies, its resurrection trigger tries to place a counter on it, but Blightbeetle's static text stops that counter from ever being placed. Because the creature returns completely clean, you can sacrifice it over and over again to the Altar, turning a neat trick into an infinite stream of colored mana, sacrifices, and death triggers.