Otherworldly Escort, Amoeboid Changeling, Thornbite Staff, and Phantom Train

Prerequisites

• Otherworldly Escort on the battlefield
• Amoeboid Changeling on the battlefield
• Thornbite Staff on the battlefield
• Phantom Train on the battlefield

Steps

1. Activate Amoeboid Changeling's second ability by tapping it, causing Otherworldly Escort to lose all creature types until end of turn
2. Activate Phantom Train by sacrificing Otherworldly Escort
3. When Otherworldly Escort dies, it and Amoeboid Changeling trigger
4. Resolve the Amoeboid Changeling trigger, untapping it
5. Resolve the Otherworldly Escort trigger, returning itself from your graveyard to the battlefield as a Spirit Detective
6. Resolve the Phantom Train ability
7. Repeat

Results

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