The Rideis Passage

As seen in

Most think of crossing the Gornfar Mountains by climbing one of the narrow, treacherous passes into a more treacherous foreign land of the Selks (Rideis). But the Rideis Passage is an ancient way to go under the mountains between Sayinia and Mandoral, though it is wholly unknown to Sayinia.
It is a part of the greater network of The Burrows.

Near a surface entrance.

The passage is a uncannily round passage, approximately 12 feet in diameter, traveling in gentle undulations both laterally and vertically for miles through the earth. Glowclings grow on the stone walls with pinpricks of blue-green light, providing too little illumination to see, but enough to silhouette another person who might have entered with you.
This organism is sensitive to disruption, however, and the scholar will note a narrow dark path worn in the very center of the round tunnel. The Rideis, even when they travel en masse to invade, will travel single file through the passage to reduce contact with the faintly glowing mossy growth. Toilet areas are far apart, if used at all; it is more responsible to pack out what you brought in, and even the Rideis army will not sully the caves with its soil.
If one listens within the deceptive stillness of the passage, one will hear a sound nearly too deep for the human or Rideis ear, but it can be perceived, nearly felt instead of heard. The Voice of the Mountain, almost musical, is a sign of the health of the passage, for this is no natural cave, not with that nearly-perfectly round shape. Rideis lore does not warn against seeking the source of the sound; there is no need of such a warning. The entire population keeps a quiet anxiety for the unknowable cycles which lead to The Spawning - Basilisks, which will appear without warning.

Ecosystem

Though the passage connects the eastern and western slopes of the Gornfar Mountains , few creatures use it for travel. It is less populated by wildlife than other cave systems. The only signs of life to the layman are the bioluminescent growth and the nearly-inaudible, nearly-musical tone.

Ecosystem Cycles

No one knows the cycles of the spawning.
Well, one person says they can be known, but who would give ear to such a source? Courtesans have but a single skill, and it is /snigger/ only tangentially related to natural science.

Localized Phenomena

A bioluminescent organism, Glowclings, grows on the surfaces of the Rideis Passage.

Type

Cave System

Location under

Gornfar Mountains

Inhabiting Species

• Glowclings