The Rakshasa are known throughout the realms as evil shapeshifting fiends that infiltrate civilized societies, gathering wealth and power to themselves while devouring hapless victims whenever the opportunity arises.
There are documented incidents of Rakshasa throughout Toril, but with the different origins of the Rakshasa come different territories.
The Old Empires: In the south the Rakshasa are referred to by the clan names that these different beasts are organized into. The Al’Kursi, Al’Chazar, and N’Al’Tharune, all known as the Lost of Ravan are most prevalent in Chessenta, Mulhorand, Thay, and Unther and those lands in the immediate vicinity.
Rakshasa: The more traditional Rakshasa that haunt the rest of Faerun are believed to be evil fiends that take the form of feline humanoids, or evil spirits that possess humans and twist their bodies into a more feline form. These monsters arrive on Faerun from the Outer Planes through portals or rifts (weaknesses in the boundaries between the Material Plane and other planes) or are summoned intentionally by evil or misguided magic users.
The origins of this type of Rakshasa are unknown and as mysterious as the origins of the Multiverse itself, having arisen anywhere in the depths of the planes or on one of the other Crystal Spheres.
The Lost of Ravan: These three clans of southern Rakshasa have their origins in Murghom as the Rak’Sha or honour guard (all minor sons and daughters from allied and related noble houses of their charge) of Crown Prince Myrkul Bey Al’Kursi.
Following the disgrace and exile of the prince, the Rak’Sha that were still in Murghom were cursed by Ra himself and their forms twisted into horrific looking feline, humanoid monsters.
The now twisted Rak’Sha escaped their imprisonment sought out a curious being in the wilds of the Shaar, known as Queen Ravan. Each Rak’Sha gained strange new abilities (from their curse and from their new patron – in return for eternal servitude), they went their separate ways to found the different clans of Rakshasa in the south (the Al’Kursi, Al’Chazar, and N’Al’Tharune) and became known as the Lost of Ravan.