Benthicore, Elemental Mastery, and Xenograft

Prerequisites

• Benthicore on the battlefield
• Elemental Mastery on the battlefield
• Xenograft on the battlefield
• Elemental Mastery attached to Benthicore
• "Merfolk" chosen with Xenograft
• Benthicore does not have summoning sickness

Steps

1. Activate Benthicore by tapping it, creating five 1/1 Elemental tokens with haste that are also Merfolks due to Xenograft
2. Activate Benthicore by tapping two Elemental tokens, untapping Benthicore
3. Repeat

Results

• Infinite creature tokens with haste
• Infinite ETB