Missy + Viscera Seer + Horde Ambusher

Missy

Viscera Seer

Horde Ambusher

How it works

1. Activate Viscera Seer by sacrificing Horde Ambusher.
2. When Horde Ambusher dies, Missy's first ability triggers, returning Horde Ambusher from your graveyard to the battlefield face down as a 2/2 Cyberman artifact creature.
3. Resolve the Viscera Seer ability, causing you to scry 1.
4. Activate Horde Ambusher's morph ability by revealing a red card from your hand, turning it face up.
5. Repeat.

This loop sets up an endless cycle of sacrifice and rebirth by letting Missy intercept your creatures as they hit the graveyard, turning them right back into play face down as 2/2 Cyberman artifact creatures. You feed any creature into Viscera Seer to churn through your library with infinite scry triggers, but Horde Ambusher is the star of the show here because its morph ability allows it to turn itself face up again right on the battlefield. Once face up, you can simply sacrifice it back to Viscera Seer to trigger Missy all over again, repeating the process indefinitely.