Heartmender, Thran Vigil, and Phantom Train

Prerequisites

• Heartmender on the battlefield
• Thran Vigil on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Phantom Train by sacrificing Heartmender
2. When Heartmender 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 Heartmender
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