There are quite a few races out there who come from we don't quite know where, or we know where but we don't really go there. This is most common with creatures from the Underdark, that layer of subterranean passages that honeycomb the earth. But we have at various times come in contact with creatures from other continents (such as the Kaelra), from far below the sea (particularly during the Great Migration) and from other dimensions (such as the djinn).
the first unknown race that has to come to mind are the Kaelra. The Kaelra stand about 7 feet tall, with very pale skin and a light blue hair. All their pigments, including nails and lips appear bleached and blue. Furthermore they are very resistant to cold, which suggests a far southern (or northern) homeland. Although there was extensive contact with them during the war there is still very little known about their customs or home. About 100 years after the Great Migration there was a great move to find their homeland and send conquering fleets after them. Ships ranged far and wide, eventually spotting a winter continent to the south, a vast barren taiga. But in the end every fleet sent after them was annihilated, although there were never any reprisals. Since then Kaelra have sent sporadic emissaries and trading vessels to the New World, but the Kaelra are hated and reviled by Dagati everywhere. Kaelra are not safe anywhere without a heavy escort and in many states their very existence is against the law. To this day they still refuse to speak of their reasons for the invasion and destruction of the Old World.
The Dwarves are an enigmatic race. They are greedy, hard-hearted, hot-tempered, violent, and selfish. The Sorvanni repeatedly tried to wipe them out of their cave warrens and repeatedly failed. However despite their obvious superiority the Dwarves never retaliated. It was thought that when the Old World sunk they disappeared forever. But lo and behold, they also had established footholds in the New World. Apparently their cave systems even went underneath the oceans and spanned continents. The Dwarves appear to be unconcerned with surface doings, only interested in us as a source of gold. But they are perpetually talking of the ongoing warfare between them and the mind-flayers, who seem to be a race of mentally powerful slavers. They also mention svirfnevblin who are Trein'lae offshoots who live underground. They speak of many other fantastic races too, most of whom have never even been seen by a Dagati much less documented.
There is a profusion of life on the ocean floor (actually most of it is between land and the continental shelf but anyway). Very little contact is had with these creatures of the sea, beyond chance encounters by seafarers. But sahuagin (fish-men), mermaids, and Lasai (what normal DnD calls sea elves) are not just creatures of myth, their existence is known of and confirmed repeatedly. There are also darker denizens of the sea, such as the infamous Kraken and the Leviathans (awakened whales).
The final mention must go to the elemental creatures who have played such a large role in Dagati history. Everyone knows that Abdari-na, king of all Efreet and virtually a god unto himself, owed a life-debt to Garadei, first Sorvanni empire. Using this life-debt the Sorvanni empire was built upon the backs of the efreet. At any one time nearly half a million efreet, elementals, salamanders, and fire-element creatures could be serving as anything from bureacrats to shock troops. It was with this utterly loyal force that the Sorvanni managed to sweep quickly and efficiently conquer the entire New World. The Kaelra also apparently invaded after making an alliance with the marid. Because of the efreet connection even today creatures from the plane of fire are often seen in Dagati lands and through them there are also a fair number of air and earth element creatures. Marid are, of course, disliked to say the least.
Aside from elemental creatures there are also various other outsiders who make their home in the upper planes and Spirit World. Examples include, celestials, demons, devils, modron, and yugoloths. These creatures are usually defined by an ideal or a cause, such as good or absolute order. They are remnants, left over from the time before the War of Elements, these creatures tend to serve either deities or elemental lords who share their beliefs. Some few, such as planetars and marilith, are their own masters. Many of them, while also serving their masters also are trying to find a way to allow Frenle to rejoin with the rest of the universe.