Thran Vigil, Phantom Train, and Persistent Constrictor

Prerequisites

• Thran Vigil on the battlefield
• Phantom Train on the battlefield
• Persistent Constrictor on the battlefield

Steps

1. Activate Phantom Train by sacrificing Persistent Constrictor
2. When Persistent Constrictor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Thran Vigil triggers, putting a +1/+1 counter on Persistent Constrictor
4. Resolve the Phantom Train ability
5. Repeat

Results

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