Elemental Mastery, and Black Carriage

Prerequisites

• Elemental Mastery on the battlefield
• Black Carriage on the battlefield

Steps

1. During your upkeep, activate Black Carriage by tapping it, creating at least four 1/1 Elemental creature tokens
2. Activate Black Carriage by paying and sacrificing an Elemental token, untapping Black Carriage
3. Repeat

Results

• Infinite creature tokens with haste
• Infinite ETB