Yarus, Roar of the Old Gods + Karlov Watchdog + Altar of Dementia + Coveted Falcon

Yarus, Roar of the Old Gods

Karlov Watchdog

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 Karlov Watchdog and causing you to draw a card.
3. During the opponent's turn, activate Altar of Dementia by sacrificing a face-down creature you control.
4. When the creature dies, Yarus's second ability triggers, returning it from your graveyard to the battlefield face-down as a 2/2 creature, and then not turning it face-up due to Karlov Watchdog.
5. Resolve the Altar of Dementia ability.
6. Repeat from step 3.

This clever loop uses Altar of Dementia to repeatedly sacrifice a face-down creature, triggering Yarus, Roar of the Old Gods to instantly recur it to the battlefield face down. Because Yarus automatically attempts to turn the recurring creature face up, the presence of Karlov Watchdog—gifted to your opponent via Coveted Falcon's face-up trigger—suppresses that flip entirely, ensuring the creature remains a face-down permanent ready to be sacrificed again. Thanks to Yarus granting your board haste and your opponent controlling the Watchdog on their turn, this engine grinds through your entire deck while milling out your opponents with infinite sacrifices.