The Neath
Vastly larger than the surface world. Referred to as the Tower or the Tree
Enter through the Faefree, Duskrealm, and Liminal City in the same way that all locations on the surface of Vega are accessible.
It is much larger than the Surface and often filled with glowing/light fogs, mists, rocks, growths, fungus
Common smaller connections to the Neath
Along the Two Seas numerous caves, often used as Pirate Bases, offer small cracks down into the Neath. Common along the Loran Coast.
Some Temples in Zund and Ghierkoth lead directly to the Neath.
Lower levels of the Endless Cities of Valeguard and Khynn-Real lower through so many levels that they eventually meld into often abandoned upper cities of the Neath
Sealed or hidden access cover many locations. Dwarves, Gnomes, and some Elven civilizations have connected the Neath and the Surface, as well as cults and organizations making connections for their own purposes. Many of these will be hidden from the uninitiated, be unfindable at certain times of day, or protected by a riddle.
There are Wandering Doors that cannot be pinpointed but are found on the Surface from time to time. They open to a staircase that can take multiple days of descent before entering the Neath. Returning up the staircase is not guarantee you will be in the same location you found it.
The Hollowed World
With its own bright sunlight this land is hot, steamy, tropical, volcanic, with seas and heavy jungles. Dinosaurs and dangerous plants are abundant.
Main access is through “the Sink,” a giant jungled abyssal sinkhole taking up much of the interior of Jirai and lowering into the Hollowed World
Main access is also found through the ice mazes of P’nau. The glacial crevasses lower under the ice and eventually melt into rivers entering the Hollowed World.
The Yawn
A long dead god titan imprisoned in the mountains. Its open mouth cracks into the Surface World of Vega. The entirety of the Yawn is heavily urbanized with many overlapping civilizations down through the levels and extremities of the Yawn.
Main access is through Northern Ghierkoth. Khaaldith fortifies and protects a corridor of trade routes in and out on the northern side of the Yawn.
Dwarven Cities
Many Dwarven civilizations reach to the Surface World of Vega such as the cities in Heirch. Abandoned cities also are often reinhabited such as the Goblins of Shale who connect to the Neath through the ruins of Dwarven cities.