Rhagodessa

This primeval vermin lacks the venomous stinger or crushing claws of a scorpion, but makes up for it with its jaws - nearly a third of the creature's weight is accounted for in its powerful mandibles. These arachnids are nocturnal hunters that dwell in caverns, moving out into the surrounding countryside to seek food well after the sun has set.

Although they're all but mindless, rhagodessas are also creatures of habit. Once a rhagodessa finds a hunting ground that's fertile, it tends to remain close to its new lair. This trait makes the rhagodessa an excellent guardian; as long as it's kept relatively well-fed, a rhagodessa settles into a small cavern or underground chamber and remains content to stay there, only rarely wandering into trouble into any nearby regions.