Beast people created by the Bolgroth as an army.

Sebastian was turned, Darrian was born with it.

Thousands of Therianthrope Souls were seen in Rina's blending vision. They were in pain and chained to a stake in the skin of a giant Devil

Rina's Research:
Therianthropy is the word used to describe a humanoid beast shifting hybrid person. 
Those cursed with this can remain and look human, choosing to shift between at their own will. They also are effected by the full moon, but because of magic, but because animals are much more sensitive to shifts in gravity, and it brings out the beastial side. 
The cursed ones go on rampages during full moons, but those cursed with it can breed and pass it down.
Those born with it are called Therianseli or "Weresouls" They have the power to shift between two forms. Unlike their predecessors they can only appear as a hybrid or fully as an animal. They do not rampage on a full moon, but do shift into animal form for its entirety. 
The big debate within the Therianthrope world is the matter of their souls. Therianthropy is, in a technical sense, still a curse. It binds the soul and is (as far as anyone knows) unbreakable. The effects of a curse on someone's soul like this are still generally unexplored. 
Rina's husband Sebastian suffered from Cat-form Lycanthropy but was twisted to allow him to appear the size as a cat. Therianthropes in most cases cannot appear to be 20% larger or smaller than their humanoid form.