By setting up Prototype Portal with an imprinted Tanglepool Bridge, you can continuously churn out token copies of the bridge for a mana cost of zero. Because Tanglepool Bridge enters the battlefield tapped, Tiller Engine immediately triggers to untap it, allowing you to tap the new bridge for mana. Filigree Sages steps in to loop the process by untapping Prototype Portal, a feat made significantly cheaper thanks to Agatha of the Vile Cauldron reducing the activation cost of the Sages' ability.