Go to the Wu-Shi Academy from the Outworld portal. Then, follow the path until you reach the catapult. On the opposite side (to the right instead of left), there should be a pathway blocked by a statue. Use Fist Of Ruin on this statue (Yeah, I noticed this statue early in the game, but completely forgot about it late in the game, haha), and follow the path to the portal. When you exit this portal, run until you get to the bridge, because it will try sucking you back in. Keep going until you find the room with the red yin-yang.