Keejin are deep-earth dwellers, spending their entire existence scuttling through caves and caverns. Prospectors have even reported finding them inside huge living organisms, like large space slugs or miner's horrors. An odd filtration system enables them to breathe normally in most environments, and one sub-species even thrives in the vacuum of space. They hatch from eggs which resemble plastic tablets and reach maturity in six standard years. Also known as "cave crawlers," keejin seem separated into two distinct genders; procreation involves group gatherings followed by brief bonding. Keejin appear to be otherwise solitary, although mated pairs have been encountered if there are hatchlings about. When settlers of any kind move into a cavern complex, resident keejin quickly leave.

Cave crawlers pick their way slowly across cave walls and ceilings with their claws and tails. The distinct cracking scrape they make as they move has raised the hackles of many an explorer The difficulty of spotting a moving keejin, even in light, adds to their disconcerting presence. Keejin hides are coarse and mottled, reflecting the colors of their native caves. The beasts flee from bright light, and so are most often encountered in dim light or darkness. Because of subterranean echoes, scouts can often hear a keejin long before they see it. Tales have been told of unnerving journeys into unexplored caverns during spawning season, when dozens or even hundreds of keejin scuttle about, all out of sight but nonetheless audible.

Various subterranean plants and small animals make up a keejin's diet. The cave crawler pries them off of the walls with short feeding tentacles and carries them to the gaping mouth located on the creature's back, between its "shoulders." Some large species of keejin have expanded their feeding stock: two documented reports state that large keejin, over two meters long, dropped from cave roofs and attacked scouting parties. While most cave crawler species have been proven harmless, these reports of more aggressive cousins adds a disturbing menace to an otherwise docile being.

Keejin tails provide both locomotion and sensory input; these tails end in bulbous organ clusters that detect changes in temperature, sound, and tactile vibrations. Although the creatures are visually blind, they retreat when confronted with strong light sources. Perhaps these sensory organs are so sensitive that the minor heat of a light-beam disturbs them. Then again, the shy creatures may simply run away when confronted with beings larger than themselves. This latter theory does not hold up well if one considers the two hostile encounters mentioned above, but makes sense in light of most keejins' behavior patterns.

Cave crawlers, then, are for the most part a nuisance, if a disconcerting one. The possibility exists, however, for there to be a larger more dangerous variety of keejin. In any case, the raspy echoes of keejin claws continues to haunt explorers in deep unsettled caves across the galaxy.