Lurking Roper, Cryptolith Rite, Judge of Currents, and Xenograft

Prerequisites

• Lurking Roper on the battlefield
• Cryptolith Rite on the battlefield
• Judge of Currents on the battlefield
• Xenograft on the battlefield
• Lurking Roper does not have summoning sickness
• "Merfolk" chosen with Xenograft

Steps

1. Activate Lurking Roper by tapping it, adding one mana of any color
2. Judge of Currents triggers, causing you to gain 1 life
3. Lurking Roper triggers, untapping itself
4. Repeat

Results

• Infinite colored mana
• Infinite lifegain
• Infinite lifegain triggers