Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Geralf's Messenger, and Phantom Train

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Geralf's Messenger on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Phantom Train by sacrificing Geralf's Messenger When Geralf's Messenger dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
2. When Geralf's Messenger enters, it triggers, causing an opponent to lose 2 life
3. Activate Phantom Train by sacrificing Geralf's Messenger When Geralf's Messenger dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. When Geralf's Messenger enters, it triggers, causing an opponent to lose 2 life
5. Resolve both Phantom Train abilities from step 1 and 4
6. Repeat

Results

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