Yarus, Roar of the Old Gods, Karlov Watchdog, Zedruu the Greathearted, and Yahenni, Undying Partisan

Prerequisites

• Yarus, Roar of the Old Gods on the battlefield
• Karlov Watchdog on the battlefield
• Zedruu the Greathearted on the battlefield
• Yahenni, Undying Partisan on the battlefield
• You control a face-down creature whose front face is a permanent card
• available

Steps

1. Activate Zedruu by paying , giving control of Karlov Watchdog to an opponent
2. During the opponent's turn, activate Yahenni 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. Resolve the Yahenni ability
5. Repeat from step 2

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers