Mikaeus, the Unhallowed, Defiant Greatmaw, and Phantom Train

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Defiant Greatmaw on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Phantom Train by sacrificing Defiant Greatmaw
2. When Defiant Greatmaw dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
3. When Defiant Greatmaw enters the battlefield, its first ability triggers, putting two -1/-1 counters on it
4. Defiant Greatmaw's second ability triggers, removing a -1/-1 counter from another creature you control
5. Resolve the Phantom Train ability from step 1 Repeat

Results

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