In ancient times, the planet was the homeworld of the ancient race known as the Precursors or Kathol (also spelled Cthol), and it shared the Kathol system with several other worlds, and the two massive launch gates, hyperspace portals that the Precursors had used to colonize many nearby systems.
At some point during the Galactic Republic, more than a thousand years before the Battle of Yavin, a Dark Jedi attempted to seize control of the native biotech, and in particular the Force-manipulating device known as the Codex. The resulting conflict led to the cataclysmic destruction of one of the launch gates, ravaging the planet Kathol and the surrounding space.
Apparently anticipating just such a contingency, the native Kathol had prepared a device which could store their life energy and intellects in non-corporeal form. A number of them managed to survive the energy surge by fleeing into this Lifewell, leaving a caretaker creature to maintain and restore their world in their absence, with the assistance of their arachnid servitor species, the Charr Ontee. The task of reviving the Precursors themselves was entrusted to the female Human Jedi Knight named Halbret, who had led a group of Jedi against the invading Dark Jedi, and entered a long-term hibernation trance after helping the Precursors enter the Lifewell.
However, the caretaker creature grew content with the power the Precursors had bequeathed to it. The creature—later known as DarkStryder—kept the disembodied Precursors trapped in the Lifewell, placed Halbret in a stasis tube to prevent her awaking, and ruled Kathol as a tyrant until defeated and destroyed in the early years of the New Republic.
By this time, Kathol was home to a bewildering variety of sentient lifeforms. There were the Charr Ontee, who had remained largely loyal to their masters' memory, and who were also the parent race of the Charon, and also the Fiery Ones, energy-beings who had appeared after the Rift Disaster, and may have been in some way related to the Kathol. But there were also a variety of new servitor species created by DarkStryder for its own purposes, or simply its own amusement—the worm-like Segmi and amorphous Maoi, the arachnid Krakai and Ssamb, the canine warrior Yapi, the arachnoid/avian Zizimaak, and a race of stunted humanoid slaves bred from Kathol stock, known as the Yimi or "Servants."
Over time, the presence of the living energy of the ancient Kathol in the Lifewell had become inexorably intertwined with the wider Force energy-field on the planet, and transformed it into what became known as the Ta-Ree, which all the native sentients could use to some extent.
Kathol had three continents, of which the most important was the northern continent, where the ancient Kathol capital had been built; by the time of the New Republic, this metropolis had decayed, leaving only the bony skeletons of organic skyscrapers, plus DarkStryder's fortress above the Lifewell, and the haphazard terraforming carried out by the Charr Ontee. To the west of the northern continent was the Zizimak Archipelago, a chain of tall, volcanic spires which were the center of the bird-arachnoid Zizimak civilization, and beyond this lay the western wasteland, more sparsely-populated, and shared between Zizimak and Segmi groups. The southern wasteland, to the south of the central sea, was almost deserted, but it was home to a Charr Ontee enclave and a "hive" of Fiery Ones (perhaps the central home of that species), while the southern polar ice-cap was home to a rogue tribe of Yapi.