The Shrine of Chaos
The heartpiece of the underground city of Skullcrusher is the Shrine of Chaos, also known as the Grand Shrine of Chaos. It is the central place of the chaos-part of the religion of the Ophidians. The shrine also houses the Wall of Lights of Chaos, enabling the Chaos Hierophant to consult the Chaos Serpent in the void.
After all followers of Chaos were slaughtered in the War of Imbalance, the Shrine became forgotten. Centuries later, the Avatar used this place to fuse the Banes of Chaos back together into the Chaos Serpent, using the Wall of Lights to return it to the void.