Oathkeeper, Takeno's Daisho, Phantom Train, and Swordsman, Sharp Scoundrel

Prerequisites

• Oathkeeper, Takeno's Daisho on the battlefield
• Phantom Train on the battlefield
• Swordsman, Sharp Scoundrel on the battlefield

Steps

1. Activate Phantom Train by sacrificing the creature with changeling
2. When that creature dies, Oathkeeper triggers, returning it from your graveyard to the battlefield
3. When that creature enters, Swordsman triggers, allowing you to attach Oathkeeper to that creature
4. Resolve the Phantom Train ability
5. Repeat

Results

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