In the eastern Tusk Mountains of the Realm of the Mammoth Lords lies a deep pit that resembles an inverted 13-layer ziggurat. The layers are littered with the bones of massive animals; and the lower the layer, the larger the bones, until they dwarf those of the largest creatures known to walk the surface of Golarion today.
At the bottom of this pit is an opening just large enough to admit an average-sized humanoid, known as the Earthnavel, or sipapu to the local Kellid tribes. Below it stretch miles of freezing-cold tunnels which lead down into Nar-Voth, the upper layer of the Darklands. These passages show signs of collapse, suggesting that there may have once been larger tunnels here that extended beneath Nar-Voth into the deeper Darklands. It is possible many large beasts of the Tolguth in the Realm of the Mammoth Lords migrated there from Deep Tolguth in Orv via now-collapsed tunnels.
The Earthnavel is guarded not only by large, terrible beasts, but also by the ghosts of fur-clad warriors from a bygone age. They attack those who do not have the proper totems and perform the proper rituals. Some also claim that the tunnels are inhabited by a race of intelligent, advanced troglodytes.