Weight of Riches
Abeir is one part of the prehistoric planet called Abeir-Toril. After the Primordials created this world, the gods interfered by wanting to create living beings to live on Abeir-Toril. This sparked a war of unbelievable destruction which ended when Ao separated the world into Abeir and Toril, each located in their own material plane. The gods ruled Toril, the primordials Abeir.
Abeir is similar to Toril in many ways, though obviously changed due to its different history. However, like Toril it contains Underdark inhabited by drow, and it is home to most of the races that inhabit Toril.
During the event called the Spellplague both worlds merged for a certain time. Now almost a quarter of what used to be Abeir lies on Toril, and vice versa — which means that, for instance, Maztica still exists and some members of the Golden Legion are trapped in Abeir.
The largest part of Abeir on Toril lies off the Sword Coast, in the Trackless Sea and is ruled by Dragons though their slaves include humans, dwarves, dragonborn, and, more rarely Tel’Quessir. The slave races are very rarely given to rebellion.