This crafty loop hinges on the non-legendary copy effect of Spark Double, which allows it to enter the battlefield as a non-legendary clone of Avatar Kuruk (the back face of The Legend of Kuruk) without violating the legend rule. Because this copy retains the terrifying Exhaust waterbend ability, you can invest into its massive mana requirement—subsidized heavily by tapping down your own artifacts and creatures—to take an extra turn. From there, Deadeye Navigator steps in as the ultimate enabler, using its soulbond pairing to grant the cloned Avatar Kuruk a reliable blink activation for just {1}{U}. Blinking the clone resets it so that when it returns to the battlefield, it re-enters anew as Avatar Kuruk, instantly re-establishing its soulbond with Deadeye Navigator and setting you up to repeat the entire sequence indefinitely for infinite turns.