Um, just gonna toss in that Taheen ain't restricted to animal head/human body but also animal body/human head.
They were genetically engineered by the Great Old Ones from a mixture of human and animal material.
They are descended partly from the prim folk (i.e demons), and partly from humanity (please clarify)
They were created by the prim folk either directly or indirectly. (Please clarify)
They come from another level of the tower, i.e. another world altogether.
They're just another kind of mutant, a result of the devastating wars much like the slow mutants.
They're from todash space, i.e. between worlds.
Possibly a combination, or partial combination above options (please clarify which ones)
None of the above, they're something completely different.
Um, just gonna toss in that Taheen ain't restricted to animal head/human body but also animal body/human head.