A book that I'm currently writing called Surge features an enemy faction called the Degenerates that are heavily inspired by the Scythians (Indo-Iranian horse nomads that ruled the Eurasian Steppe and Central Asia from the 9th century BC to the 1st century CE) and consists mostly of humans parasitized by a prehistoric worm-like endoparasite called Echidna, which parasitizes and radically alters the entire physiology of a wide variety of organisms from the phylum Chordata.
Parasitized humans are transformed into nocturnal humanoids that are facultative quadrupedals and divided into three distinct subspecies, named after the sons of Hercules and Echidna (all of which were ancestors of the Scythians):
Agathyrsus (Physically imposing and immensely strong Degenerates used mostly as shock troops, cataphracts and heavy infantry)
Gelonus (Lightly-built and multi-armed Degenerates which act as scouts, light infantry and cavalry whose purpose is to advance beyond their own front lines for the intent of harassing enemies from afar)
Scythes (Degenerates that have excellent vision and are deployed as marksmen and mounted riflemen, who engage their targets at long range).
Human-spawned Degenerates can only reproduce by giving live birth to thousands of Echidnae that are used to convert more humans into potential Degenerates, due to the Echidnae hijacking their reproductive system. Because of this, Degenerates are constantly capturing humans to use as hosts and have compact skulls with specialized jaws that can grasp and carry envenomated humans by the neck, allowing them to be brought underground for conversion. I have no idea what sort of jaws such a creature would have, especially ones that have teeth for consuming plants and meat along with a set of myotoxic fangs used to paralyse humans.