Stalwart Successor, Glen Elendra Archmage, and Phantom Train

Prerequisites

• Stalwart Successor on the battlefield
• Glen Elendra Archmage on the battlefield
• Phantom Train on the battlefield

Steps

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

Results

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