The Phon'Qi Caverns, alternatively known as Phon'Qi's Caverns, represent a network of subterranean caves situated beneath the Rambler's Reach Outpost and the adjacent Foothill Falls region of Koboh, a planet located in the Outer Rim. These caverns served as a habitat for diverse and peculiar native lifeforms, notably various fungal varieties. The name of the caverns originates from Phon'Qi, a priorite seeker who rediscovered them after their abandonment during the High Republic Era. During the period when the Galactic Republic and the Jedi Order were investigating the Koboh Abyss and the planet Koboh, they established a small base within the caverns. This installation was intended for monitoring planetary activity and studying the unique fungal life. It is recorded that a contemplative Jedi Padawan once remarked on the irony of studying the stars from below ground, an observation that prompted a gentle scolding from her master. Following the descent of Jedi Dagan Gera to the dark side of the Force, Rayvis, a Gen'Dai warrior loyal to Gera, relentlessly searched the caverns for information about his master's location, slaughtering a number of Jedi and Padawans in his pursuit. Their corpses were disrespectfully left within the caves.
By 9 BBY, Rayvis, failing to locate his master, and his band of Bedlam Raiders had solidified their presence in the caverns, continuing their quest for clues. The Raiders strategically positioned some of their re-programmed Separatist battle droids throughout the cavern system. They also constructed a modest depot within the caves, repurposing Republic facilities to support their operations. This depot was used to store droid components, armaments, and other provisions.
The caverns presented considerable danger to Koboh prospectors who ventured into the labyrinthine passages. The native bulbous fungi, which had evolved mouths, tongues, and tactile sensitivity, possessed the ability to detonate, releasing highly potent acid capable of rapidly dissolving metal. These fungi also emitted a pungent acidic smell. Aside from the flora, the presence of the Bedlam Raiders posed a significant threat. Sometime before 9 BBY, a rancor established its lair within the caverns. While some theorized that the Bedlam Raiders had attracted it, the Raiders undeniably provided the rancor with a consistent supply of humanoid prey to consume.
Additional infrastructure within the Phon'Qi Caverns included a system of turbolifts and an intricate network of scaffolding and structures that linked the various excavation sites.