This fascinating loop turns the conventional rules of Magic completely on their head, letting you take infinite turns by weaponizing the very bottom of your library. When you cast Capture of Jingzhou, it heads straight to the graveyard after resolving, only to be scooped back up and placed on the bottom of your deck by Epitaph Golem's activated ability. Normally, drawing from the bottom would require special setup, but River Song completely redefines the rules of the game by forcing you to draw from the bottom instead of the top. By feeding the extra-turn spell back into your library with Epitaph Golem and immediately drawing it off the bottom thanks to River Song during your draw step, you seamlessly chain Capture of Jingzhou over and over again into an unstoppable succession of infinite turns.