Valkyrie's Call, Amoeboid Changeling, Spawning Pit, and Glamermite

Prerequisites

• Valkyrie's Call on the battlefield
• Amoeboid Changeling on the battlefield
• Spawning Pit on the battlefield
• Glamermite on the battlefield

Steps

1. Activate Amoeboid Changeling's second ability by tapping it, removing all creature types from Glamermite
2. Activate Spawning Pit by sacrificing Glamermite
3. When Glamermite dies, Valkyrie's Call triggers, returning Glamermite from your graveyard to the battlefield as an Angel with flying and a +1/+1 counter on it
4. When Glamermite enters the battlefield, it triggers, untapping Amoeboid Changeling
5. Resolve the Spawning Pit ability, putting a charge counter on it
6. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite charge counters on a permanent
• Infinite death triggers
• Infinite sacrifice triggers