Mabari war hounds are a breed of dogs magically bred by the Formari. Each mabari chooses their master for life in a process called imprinting. Although fierce combatants, a mabari companion is shown to be a highly sociable animal, and though not capable of speech, they can clearly respond to speech with growls, whines, barks and several other actions that demonstrate intelligent comprehension.
Mabari are often used in battle, and to defend noble properties. To help differentiate their dogs when in battle, kaddis is used by mabari handlers.
In Dragon Age: Origins, the Warden may be fortunate enough to have a mabari dog join their party, either by virtue of being high-born, or by helping to care for a sick dog at Ostagar. After the battle, the dog will find the party on the road, slightly ahead of a horde of pursuing darkspawn.
Even the dog is not accepted after Ostagar, the Return to Ostagar DLC affords the Warden another opportunity; the mabari will be revealed to have survived the darkspawn infestation and will be alive and willing to accompany the party.