Doppelgang + Echo Mage + Corridor Monitor

Doppelgang

Echo Mage

Corridor Monitor

How it works

1. Cast Doppelgang by paying 6, 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.

This brilliant loop transforms a high-mana investment into an overwhelming cascade by leveraging Echo Mage at level 4+, whose ability to copy spells twice lets you replicate a massive Doppelgang. When Doppelgang resolves to duplicate your permanents—including a mana producer and Corridor Monitor—the resulting Corridor Monitor tokens trigger to untap both the mana source and your heavily-leveled Echo Mage. This leaves you ready to tap the newly created token mana sources and feed Echo Mage's {U}{U} activation cost all over again. By chaining these copies together, you rapidly multiply your board state into an endless sea of tokens, infinite mana, and infinite triggers.