Elemental Mastery, Brimstone Trebuchet, and Arcane Adaptation

Prerequisites

• Elemental Mastery on the battlefield
• Brimstone Trebuchet on the battlefield
• Arcane Adaptation on the battlefield
• Elemental Mastery attached to Brimstone Trebuchet
• Brimstone Trebuchet does not have summoning sickness
• "Knight" chosen with Arcane Adaptation

Steps

1. Activate Brimstone Trebuchet by tapping it, creating a 1/1 Elemental creature token
2. The Elemental enters the battlefield as a Knight due to Arcane Adaptation, triggering Brimstone Trebuchet, untapping Brimstone Trebuchet
3. Repeat

Results

• Infinite creature tokens with haste
• Infinite ETB