The beast was actually pretty weak, easily killed with a simple attack by Farhad, who dragged his arm out of the squirming corpse while looking at the beast with some disgust.
"This is problematic, call Sergeants we have to inform them of a new mutant."
Usually, ghouls are slow when digging, just like a simple mouse or rabbit, they take time to dig and are generally unable to know what's above them, It is why their tunnels are so wild and the only correct direction they know is going up or going down, nothing else matters.
But what of this simple beast?
It accurately found a target below ground and tried to harm it, which just happened to be what killed it in the first place.
But this sets a display of its capabilities, and how dangerous it can be to find a path toward human civilization. A path that other ghouls can follow.