Stalwart Successor, and Phantom Train

Prerequisites

• Stalwart Successor on the battlefield
• Phantom Train on the battlefield

Steps

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

Results

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