Xing and Xang are once the Good and Bad Angels of Lore, Xing and Xang became the Second Lords of Chaos when Drakath got hold of them. As revealed during the Bloodtusk saga, Drakath replaced the good Xang with her Mirror Realm opposite, making both of the Angels evil. They are the only Chaos Lords not to have been fought and defeated.
They are the most prominent of the 13 Chaos Lords, and are currently at Drakath's side. They spend their time turning people to the side of Chaos with their manipulative words. It's later revealed in the Bloodtusk Ravine saga that Drakath switched the place of the main world's good Xang with the Mirror Realm's evil Xang.
After finding all parts of the cube, the player returns to Mobius, to build the Runix cube, through a minigame. After this the player has to invade Escherion's inverted tower, and use the cube to destroy him. However once the player arrives, he finds out that the only thing that could stop Escherion's plans for that region was if he did not find the cube. After a short dialogue, Escherion throws the player out of his tower, and summons the Lake Hydra from the lake.