Thessalmonster

Thessalmonsters were a class of monstrosities found on Toril. Each of the four types of thessalmonster were hybrids created from crossbreeding between various monsters and thessalhydrae, which in turn had descended from an original, extinct ancestor creature&mdash;also called a thesselmonster&mdash;known for its ability to freely crossbreed with other monsters.

Description
While each of the four types of thessalmonsters varied in appearance, size, and temperament, they also shared certain features. They all had large, reptilian bodies and multiple heads. They all also were active at night or in the dark, and preferred damp environments.

Subspecies

 * Thessalhydra:The creatures said to be most similar to the original thessalmonsters, these were hybrids between thessalmonsters and hydrae.
 * Thessalmera:Hybrids produced as offspring between a thessalhydra and a chimera.
 * Thessalgorgon:Hybrids produced as offspring between a thessalhydra and a gorgon.
 * Thessaltrice:Hybrids produced as offspring between a thessalhydra and a cockatrice.

History
The original thessalmonsters from which the above subspecies descended were extinct by the 14 century DR, and as of this time, the origin of the name "thessal" had also been lost. It was believed to have referred either to the lands in which thessalmonsters were first observed or to the person or faction responsible for creating them.

The original thessalmonsters were renowned for their genetic instability, which allowed them to crossbreed with a wide range of different monsters. These ancestral thessalmonsters were said to have resembled thessalhydrae, except lacking the hydra-derived crown of multiple heads. This means they would have appeared as reptiles with circular mouths rimmed with teeth and an  tail tipped with a pair of sharp pincers. Their coloration would have been dark green with yellow splotches and the occasional tuft of reddish hair.