Ghast

The Ghast is a short creature that dwells within the mountain caverns of Thedas. Though individually small and timid, they are surprisingly vicious when encountered in large numbers.

Background

Taking shelter in various mountain caves and rarely venturing to the surface, ghasts are highly territorial creatures who live together in packs. If they have sufficient numbers, they will drive away or even kill those who encroach on their territory with malicious fervor. They technically are subterranean creatures, but it should be made clear that they are not creatures of the Deep Roads.
While they are cunning and have a basic understanding of cooperation, ghasts aren't considered truly intelligence beings, as they are incapable of speech. They communicate only through grunts and squeals. As well, it's possible that they are smart enough to be able to craft spear-like weapons from stone though most believe that these weapons were either found by the ghasts or were things taken from those whom they have attacked.
Some theorists hold the belief that these things were once slaves of the Tevinter Imperium who were experimented upon. These ideas are baseless, though that doesn't stop some from believing.

Additional Information

Perception and Sensory Capabilities

Occasionally, a pack of ghasts will include the strange creature known as the velghastrial. Unlike the common ghast, the velghastrial can wield magic. Some assume that they first learned by lurking around and watching other mages. Others believe that ghasts, like animals, are sensitive to the unseen forces that shape our world and that the velghastrial is able to utilize magic purely through instinct. It is unknown if velghastrials risk possession when casting spells, as other humanoid mages do.