All 30 Combos with Mountain Valley

Kodama of the East Tree + Ghost Town + Omnath, Locus of Rage + Mountain Valley

Infinite Mana: Infinite colorless mana, Infinite creature ETB, Infinite creature tokens, Infinite landfall triggers

Fetch a land using Mountain Valley. When the fetched land enters, Omnath and Kodama trigger. Resolve the Kodama trigger, putting Ghost Town from your hand onto the battlefield. When Ghost Town enters, Kodama and Omnath trigger. Holding priority, activate Ghost Town's first abiltiy by tapping it, adding {C}. Activate Ghost Town's second ability by paying {0}, returning it from the battlefield to your hand. Resolve the Omnath from step 4, creating a token. When the token enters, Kodama triggers, putting Ghost Town from your hand onto the battlefield. When Ghost Town enters, Omnath triggers. Repeat from step 5.

Cards: Kodama of the East Tree, Ghost Town