Yarus, Roar of the Old Gods + Karlov Watchdog + Phyrexian Altar + Bilbo, Luckwearer // Burglar's Plot

Yarus, Roar of the Old Gods

Karlov Watchdog

Phyrexian Altar

Bilbo, Luckwearer // Burglar's Plot

How it works

1. Donate Karlov Watchdog to an opponent.
2. During the opponent's turn, activate Phyrexian Altar by sacrificing a face-down creature you control.
3. 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.
4. Repeat from step 2.

This intricate loop relies on trading away your own defenses with Bilbo, Luckwearer // Burglar's Plot to saddle an opponent with Karlov Watchdog, whose static ability ensures your morphs stay stubbornly face-down when they return. Once that lockdown is in place, you can feed a face-down creature to Phyrexian Altar for any color of mana, triggering Yarus, Roar of the Old Gods to immediately loop the creature back onto the battlefield from the graveyard. Thanks to Karlov Watchdog stopping the card from turning face up, Yarus's delayed flip condition never completes its cycle in a way that breaks the loop, letting you repeat this sacrifice engine indefinitely for an infinite stream of triggers and mana.