Lurking Roper, Elemental Mastery, and Verdant Sun's Avatar

Prerequisites

• Lurking Roper on the battlefield
• Elemental Mastery on the battlefield
• Verdant Sun's Avatar on the battlefield
• Lurking Roper does not have summoning sickness
• Elemental Mastery attached to Lurking Roper

Steps

1. Activate Lurking Roper by tapping it, creating four 1/1 Elemental creature tokens
2. When the Elementals enter the battlefield, they trigger Verdant Sun's Avatar four times
3. Resolve the first Verdant Sun's Avatar trigger, causing you to gain one life
4. Lurking Roper triggers, untapping itself
5. Repeat

Results

• Infinite creature tokens with haste
• Infinite ETB
• Infinite lifegain
• Infinite lifegain triggers