Orah, Skyclave Hierophant, Sister Hospitaller, Morophon, the Boundless, and Phantom Train

Prerequisites

• Orah, Skyclave Hierophant on the battlefield
• Sister Hospitaller in the graveyard
• Morophon, the Boundless on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Phantom Train by sacrificing Morophon
2. When Morophon dies, Orah triggers, returning Sister Hospitaller from your graveyard to the battlefield
3. When Sister Hospitaller enters, it triggers, returning Morophon from your graveyard to the battlefield and causing you to gain 7 life
4. Resolve the Phantom Train ability
5. Activate Phantom Train by sacrificing Sister Hospitaller
6. When Sister Hospitaller dies, Orah triggers, allowing you to return a Cleric with mana value 5 or less from your graveyard to the battlefield
7. Resolve the Phantom Train ability
8. Repeat

Results

• Infinite lifegain
• Infinite recursion of some creature cards in your graveyard
• Infinite sacrifice triggers
• Infinite +1/+1 counters on a creature
• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite lifegain triggers