Sunstrike Legionnaire, and Elemental Mastery

Prerequisites

• Sunstrike Legionnaire on the battlefield
• Elemental Mastery on the battlefield
• Elemental Mastery attached to Sunstrike Legionnaire
• Sunstrike Legionnaire does not have summoning sickness

Steps

1. Activate Sunstrike Legionnaire by tapping it, creating a 1/1 Elemental creature token with haste
2. When the Elemental enters the battlefield, Sunstrike Legionnaire triggers, untapping it
3. Repeat

Results

• Infinite creature tokens with haste
• Infinite ETB