Hallcrawlers
These Hydrette forms slither through the vents with compressible bodies to ambush and try to decapitate whatever is unfortunate enough to encounter them in the ruins of Valoo. No one knows where these creatures were 'designed' or where they are originally from, but they are not natural and have no known record outside of Waimana Valley.
They still retain the reptilian appearance of other Hydrettes, but shrunken down to the size of a large wolf. The usual snake like body has been augmented with a fan of tentacles that probe out in all directions from the beast. The scraping of its teeth against the vents it is in may be the only hint of their presence.
To aid in capture of prey, the Crawlers limbs are capable of delivering a cytotoxic venom. It will wrap its limbs around its prey and attempt to drag limbs into its hiding spot to attack and dismember.
A Sinister Thing
Hallcrawlers are treated like bogeymen to the people of Kainga. Many of the older generation still remember losing several children to Hallcrawlers during the early days. Now a days they are kept sealed below by the collapse of the floors.
If you hear hissing and see no Hydrette, barricade yourself. Leave no space large enough for your leg to be pulled through... And be ready with a blade.
Awesome! I particularly loved that you used sound as a sensory detail ("The scraping of its teeth against the vents it is in may be the only hint of their presence."). I don't feel like enough of us remember to do that in our writing. Sound and smell are hard to write, but they can do so much! And I will not soon forget the shiver that ran down my spine when I imagined the sound of this creature's teeth scraping against the vents.
They are an absolute challenge to write, I'm still having to learn a lot of the 'spicy' ways that you can communicate a sense through writing. I'm glad I got you with a shiver, as anyone should we having to deal with these beasts.