Saffi Eriksdotter, Mistmoon Griffin, and Phantom Train

Prerequisites

• Saffi Eriksdotter on the battlefield
• Mistmoon Griffin on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Saffi by sacrificing it, targeting Mistmoon Griffin
2. Activate Phantom Train by sacrificing Mistmoon Griffin
3. When Mistmoon Griffin dies, it and Saffi trigger
4. Resolve the Saffi trigger, returning Mistmoon Griffin from your graveyard to the battlefield
5. Resolve the Mistmoon Griffin trigger, failing to exile it as it is not in your graveyard and then returning Saffi from your graveyard to the battlefield
6. Resolve the Phantom Train ability
7. Repeat

Results

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