I'm tempted to say +0 because its art shows it as a tool-using humanoid, even with bracers that don't completely clasp around its arms. The stat penalties sort of suck, but the save or lose helps to balance that. Sonic vulnerability does really suck, but there's ways to counter it. Silence can cover your butt if you're really scared.

I also want to give these guys +0 to set them apart from the crappy bat-people, Desmodu. At least a Nycter tries to be bat-like and doesn't have some Munchausen pole-weapon for some reason.