I think that the most fearsome attribute of these awesome creatures is their silence and the fact that one never sees them--nothing but those baleful eyes glaring unblinkingly out of the dark void behind.
Grasping my long-sword tightly in my hand, I backed slowly along the corridor away from the thing that watched me, but ever as I retreated the eyes advanced, nor was there any sound, not even the sound of breathing, except the occasional shuffling sound as of the dragging of a dead limb, that had first attracted my attention.
On and on I went, but I could not escape my sinister pursuer.
Suddenly I heard the shuffling noise at my right, and, looking, saw another pair of eyes, evidently approaching from an intersecting corridor. As I started to renew my slow retreat I heard the noise repeated behind me, and then before I could turn I heard it again at my left.
The things were all about me. They had me surrounded at the intersection of two corridors. Retreat was cut off in all directions, unless I chose to charge one of the beasts.