Nexus

According to Thorgrim, a nexus exists in multiple places at the same time, allowing a person to go between these different locations merely by visiting.

Will certainly not be as easy as that.

Certain Nexuses:

• In North Africa there is a dungeon that was populated by drow. In the basement there was a pool. Swimming through the pool took Slith and Nakula to another cave in a different part of Africa. There were Pygmies there, so it may be near Kor.
• Heliodorus uses bathhouses throughout the Roman Empire for instantaneous travel.

Possible Nexuses include:

• The Glitter Gates
• The Marshan Veldt
• The so-called Gateways to Hell. There are three of these around the world that are known: one under Scotland in Asophus' dungeon, one under the Lost Elven City that Esthalin controls, and one under the Sea of Glass, in the Temple of Elven Gods.

When Orm's Moorish Allies went into the Marshan Veldt, they said reality started to warp around them strangely and they quickly exited in fear. Harald reports the same thing when the Following Alexander Party started walking into the Gateway located under the Sea of Glass. Perhaps this is how a Nexus bridges space: by bending and twisting reality. Both of these possible Nexuses were guarded by strange and powerful monsters.

The Gateways to Hell don't go to Hell at all: they go to the Abyss. Monsters don't guard the Gateway so much as they live in the freakin' Abyss, and don't take kindly to strangers intruding on their turf.