Metamorphosis Fanatic, Phantom Train, and Felidar Guardian

Prerequisites

• Metamorphosis Fanatic on the battlefield
• Phantom Train on the battlefield
• Felidar Guardian in hand

Steps

1. Cast Felidar Guardian by paying its mana cost
2. When Felidar Guardian enters the battlefield, it triggers, targeting Metamorphosis Fanatic
3. Holding priority, activate Phantom Train by sacrificing Felidar Guardian
4. Resolve the Felidar Guardian ability, blinking Metamorphosis Fanatic
5. When Metamorphosis Fanatic enters the battlefield, it triggers, returning Felidar Guardian from your graveyard to the battlefield
6. Repeat from step 2

Results

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