Doppelgang, Echo Mage, and Corridor Monitor

Prerequisites

• Doppelgang in hand
• Echo Mage on the battlefield
• Corridor Monitor on the battlefield
• available

Steps

1. Cast Doppelgang by paying , targeting Corridor Monitor and a mana-producing permanent
2. Holding priority, activate Echo Mage by paying and tapping it, copying Doppelgang, targeting Corridor Monitor and a mana-producing permanent
3. Resolve the copy of Doppelgang, creating two copies of Corridor Monitor and the mana-producing permanent
4. When the Corridor Monitor tokens enter, they trigger, untapping Echo Mage and any other applicable permanent
5. Holding priority, activate the two mana-producing permanent tokens by tapping them, adding at least
6. Repeat from step 2

Results

• Infinite ETB
• Infinite creature tokens
• Infinite untap of creatures you control
• Infinite mana creatures you control can produce
• Infinite mana artifacts you control can produce
• Infinite magecraft triggers
• Infinite landfall triggers
• Infinite untap of artifacts you control
• Infinite copies of permanents on the battlefield