Mikaeus, the Unhallowed, Phantom Train, and Chaos Spewer

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Phantom Train on the battlefield
• Chaos Spewer on the battlefield

Steps

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

Results

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