Red Moon said:

Sure! We can have the world be dark for most of the time. Like maybe the daylight comes only for an hour or two, instead of like twelve hours.

And I like the idea that the creature only hunts at night, too. And the dogs themselves have become better suited for living in the dark, maybe. Like better night vision, etc.

As for the monster, I think it would be best if there is a single one(for now? Maybe there is only a single one that they know of. Like in their area, at least. Maybe later, more pop up). I like the idea that it is a mutation from a lab of some sort. Giving it a few mystical elements could be fun.

I love where this is going! I kind of see the creature being a dog mutation of some sort. In addition to some of the ideas already mentioned I pictured this creature having more claw-like features vs paws for its front feet. A bit larger of a head with [potentially] no ears visible ears, as well as discoloration around the upper body. Like, maybe its original form was black, and now it has some reddish blotches around the face where more visible mutations occur. [the rest of the body remaining black] Just ideas!

I do like the idea of the creature traveling alone and being territorial. As well as what Imp mentioned about there being multiple, but the group believes there is only one.