Infernal Vessel, Valkyrie's Call, and Phantom Train

Prerequisites

• Infernal Vessel on the battlefield
• Valkyrie's Call on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Phantom Train by sacrificing Infernal Vessel
2. When Infernal Vessel dies, it triggers, returning itself from your graveyard to the battlefield as a Demon in addition to its other types
3. Resolve the Phantom Train ability
4. Activate Phantom Train by sacrificing Infernal Vessel
5. When Infernal Vessel dies, Valkyrie's Call triggers, returning Infernal Vessel from your graveyard to the battlefield as an Angel in additional to its other types
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