Blightbeetle + Bloodflow Connoisseur + Harmless Offering

Blightbeetle

Bloodflow Connoisseur

Harmless Offering

How it works

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

This cunning loop turns your opponent's own defenses against them by using Harmless Offering to gift a Blightbeetle across the table, shutting down their ability to place +1/+1 counters. With that restriction locked in by Blightbeetle's passive text, you can repeatedly sacrifice an undying creature to Bloodflow Connoisseur to grow the Connoisseur into a massive threat. Because Blightbeetle prevents counters from being placed, the sacrificed creature's undying ability returns it to the battlefield clean and without counters every single time, letting you cycle the creature endlessly to farm infinite sacrifices, triggers, and counters.