Template:Castle of Grief
The Gibbet is one of the maps accessed from Hub 4: Castle of Grief (map). This is almost like a sub-hub in itself. From here, you can access Hub 4: Effluvium and Hub 4: Dungeons.
After you acquire the Axe Key after a lengthy run-around, you will be able to battle the Heresiarch for the second time. When you pass through the axe key doorr, once the chaos serpents appear, DO NOT kill them before the dark bishops are released. If all the chaos serpents are dead before the dark bishops come in, the dark bishops often never turn up, so you will have a hard time killing then to reach the Heresiarch.