Blightbeetle + Altar of Dementia + Coveted Falcon

Blightbeetle

Altar of Dementia

Coveted Falcon

How it works

1. Activate Coveted Falcon by paying 1, turning it face up.
2. Coveted Falcon triggers, causing an opponent to gain control of Blightbeetle and causing you to draw a card.
3. Activate Altar of Dementia by sacrificing the undying creature.
4. 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.
5. Resolve the Altar of Dementia ability
6. Repeat from step 3.

This intricate loop turns an opponent's loyalty against them by weaponizing the rules of ownership and counter prevention. While Altar of Dementia provides the sacrifice outlet and mills your library, Coveted Falcon acts as the vessel that repeatedly hands over your own permanents when turned face up via its disguise ability. The magic truly holds together because Blightbeetle stands watch on the battlefield: its static ability prevents opponents' creatures from ever receiving +1/+1 counters, elegantly bypassing the restriction that would normally stop an undying creature from recurring indefinitely.