Yarus, Roar of the Old Gods + Karlov Watchdog + Altar of Dementia + Harmless Offering

Prerequisites

• You control a face-down creature whose front face is a permanent card.
• You have enough mana to cast Harmless Offering.

Steps

1. 1Cast Harmless Offering by paying its mana cost, giving control of Karlov Watchdog to an opponent.
2. 2During the opponent's turn, activate Altar of Dementia by sacrificing a face-down creature you control.
3. 3When 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. 4Resolve the Altar of Dementia ability.
5. 5Repeat from step 2.

Effects

• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers
• Infinite mill
• Infinite self-mill