Find it from old release threads. Find clients that contain them, etc. Black twilight sets can be added if you have the dds from the other fourms.
Baby Behemoth can be done by:
Editing the propmover.txt. Copy a pet mover and then make your own MI and etc. Define the MI in Defineobj.h.
Then continue copying a pet from the Propitem.txt / Specitem.txt and add the name. Define it. Copy crap from the mdldyna and just rename the name on the mob part of the mdldyna of the pet you copied to the part after the mvr_ in the model name. Then edit the MI to your MI. And then edit the 1.0f or whatever it was to something significantly lower unless you want a behemoth pet to be the same size as a real one.