This clever loop hinges on circumventing the once-per-game restriction of the Exhaust ability by constantly refreshing the permanent using Brago, King Eternal's combat damage trigger. Because Sakashima of a Thousand Faces enters the battlefield as a copy of Avatar Kuruk, it inherits that formidable Waterbend ability—allowing you to leverage your artifacts and creatures to pay the massive {20} cost and take infinite extra turns. Meanwhile, Sakashima of a Thousand Faces's passive ability turns off the legend rule entirely, ensuring your copies of The Legend of Kuruk don't immediately destroy themselves, while the front face's triggered ability rewards your spellcasting with an army of unblockable Spirit tokens to help tap down for future mana.