Yarus, Roar of the Old Gods, Karlov Watchdog, Phantom Train, and Donate

Prerequisites

• Yarus, Roar of the Old Gods on the battlefield
• Karlov Watchdog on the battlefield
• Phantom Train on the battlefield
• Donate in hand
• available

Steps

1. Donate Karlov Watchdog to an opponent
2. During the opponent's turn, activate Phantom Train 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 Phantom Train ability
5. Repeat from step 2

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite +1/+1 counters on a creature