The Great Mystery
Though it's unclear if they were native to the Material Plane or came from elsewhere, the most recent of the ancient discoveries are the Sa'avi- perhaps the most advanced civilizaton as of yet discovered in Saleh'Alire. They built towering spires and gleaming cities fueled by incredibly advanced Arcane technology- the likes of which remain unrivaled by anyone as of yet (Even the yhe Nom'Yth, and their Elven descendants). They also made great strides in magical experimentation- most notably the magical genetic experimentations that produced the Khenra, Tabaxi, Dovakor, and other Beast Races ... But despite their unfathomably advanced nature, they appear to have remained strictly isolated to the continent of Tolara- showing little interest in branching out or expanding their territory. As a result, their ruins are rather rare to encounter, though several have been discovered across the continent. The Sa'avi eventually met a grim end at the hands of the very technology for which they are so well known today; the entire race was lost during an event known only as The Cataclysm around the year 3319. The exact specifics of the event still remain a mystery to Tolaran Archivists. But what is known, is that the event was related to a power source favored by the Sa'avi, and led not only to their disappearance ... But to the desolation of a large part of the southern portion of the continent and the destruction of the entire Weave itself.
It took centuries for the Weave to recover enough after The Cataclysm for magic to return to the Universe again- causing an intellectual and magical dark age from which the Universe is still recoverning to this day. But the continent of Tolara itself, specifically the area now known as the Shards, may never recover.