Shrine of Singularity
The Shrine of Singularity is located in the Holy City, the southeast region of Ter Mur immediately north of the Tomb of Kings. You can teleport into the shrine, or use a teleport scroll for any character without magery.
Here you can say the shrines mantra "unorus" which will start the Sacred Quest to gain access to the Stygian Abyss Dungeon.
You can teleport into the shrine, or use a teleport scroll for any character without magery. Teleportation point to shrine: