Horn of Gondor, Mana Echoes, Voltaic Key, and Rings of Brighthearth

Prerequisites

• Horn of Gondor on the battlefield
• Mana Echoes on the battlefield
• Voltaic Key on the battlefield
• Rings of Brighthearth on the battlefield
• available

Steps

1. Activate Horn of Gondor by paying and tapping it
2. Rings of Brighthearth triggers
3. Choose not to pay
4. Resolve the Horn of Gondor trigger, creating a number of 1/1 Human Soldier creature tokens equal to the number of Humans you control
5. When the Humans enter the battlefield, Mana Echoes triggers that many times
6. Resolve a Mana Echoes trigger, adding for each Human and/or Soldier you control
7. Repeat step 5 for each remaining trigger
8. Activate Voltaic Key by paying and tapping it, targeting itself
9. Rings of Brighthearth triggers, causing you to pay to copy Voltaic Key's ability, targeting Horn of Gondor
10. Resolve both Voltaic Key abilities, untapping it and Horn of Gondor
11. Repeat

Results

• Infinite ETB
• Infinite colorless mana
• Infinite creature tokens
• Infinite mana artifacts you control can produce
• Infinite untap of artifacts