Lamia are one of the chimeric creatures, almost certainly created by the magical transformation of beasts into unstable monsters. This magical origin means that different types of lamia have arisen independently at various different times and in different places throughout the ages of Toril, some of these types have survived and proliferated while others perished and were lost to history.
All lamia are categorized into 3 basic sub races; lamia noble, lamia, and sair, all of which arise as a result of procreation from one of the other forms. The magical instability normally inherent within chimeric creatures means that each of the subraces are unable to breed true within their own species. A lamia noble pairing gives rise to lamia, while lamia pairings give rise to sair. Monstrologists theorise that matings of part human, part animal chimeras produce more animalistic progeny, this is supported by the offspring of lamia couples being more animal than the parents and also explains why a human – lamia couple is needed to produce a lamia of the same subrace.
Old Empires Lamia
The lamia of the Old Empires region (Chessenta, Mulhorand, Thay, Unther) are most typically of reptilian stock.
Most scholars believe that an ancient reptilian – humanoid race once dominated the region long before the arrival of the Mulan and the Imaskari. This magically mighty race (according to the sage E-Bailoks of Shussel) are thought to be responsible for the creation of many different reptilian and serpentine creatures in the region and explains the unusually high number and variation of snakes in the Old Empires region.
The sarrukh did indeed create lamia like creatures (although their original creations varied greatly in form and only after millennia of breeding did it resemble todays lamia) in an attempt to merge reptilian and human traits to create a more capable servitor race that it could control like other reptiles.
The lamias were the many failures that the sarrukh created over several thousand years, discarded and allowed to run wild. The sarrukh attempt at creating a servitor race would eventually prove successful, but only in far of Merrshaulk with the Yuan-ti. The lamia meanwhile were forgotten and left to their own devices (which mostly involved feasting upon the scattered tribes of Turami humans that hid among the trees and hills of Okoth.