Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Butcher Ghoul, and Phantom Train

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Butcher Ghoul on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Phantom Train by sacrificing Butcher Ghoul When Butcher Ghoul dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
2. Resolve the Phantom Train ability
3. Activate Phantom Train by sacrificing Butcher Ghoul When Butcher Ghoul dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. Butcher Ghoul enters and dies as a state-based action due to having 0 toughness
5. Its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
6. Resolve the Phantom Train ability from step 4
7. Repeat from step 4

Results

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