Blightbeetle + Bartolomé del Presidio + Bazaar Trader

Blightbeetle

Bartolomé del Presidio

Bazaar Trader

How it works

1. Donate Blightbeetle to an opponent
2. Activate Bartolomé del Presidio 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 Bartolomé del Presidio ability.
5. Repeat from step 2.

This clever loop transforms a mechanical restriction into an infinite engine by leveraging Bazaar Trader to give your opponent control of Blightbeetle. Because Blightbeetle states that your opponents' creatures can't have +1/+1 counters put on them, it subtly sabotages the usual safety net of any undying creature you feed to Bartolomé del Presidio. When that creature dies, its undying ability normally returns it with a counter to prevent looping, but Blightbeetle's passive suppression steps in to strip away that limitation entirely. With the counter prevented, the creature returns completely clean, allowing Bartolomé del Presidio to sacrifice it over and over again to grow infinitely large while churning out endless death triggers.