MTG Combo: Retreat to Coralhelm + Simic Growth Chamber + Walking Atlas

This could be an infinite combo, however it requires two karoo lands (any land that taps for two mana and returns a land to your hand) and Amulet of Vigor. When you have all 5 pieces, this generates infinite mana and infinite landfall triggers. Simply have Retreat to Coralhelm always untap Walking Atlas or other similar creatures, and use Walking Atlas to put the karoo lands that get returned to your hand by the other karoo land onto the battlefield. They always etb untapped thanks to the Amulet of Vigor you should have on the battlefield as well, so you tap them for mana before they get returned to your hand. And voila, infinite mana.