They have lost their sentience and became ghouls, much like the blight wolves and corrupted spiders. Bereskarn are slothful creatures when left alone, but fierce and unyielding when they attack. They are often enraged and prodded into battle by the darkspawn.
Tainted bears grow larger and sprout enormous bony spikes that protrude from their fur, causing severe wounds.
Blood constantly seeps from these wounds, giving bereskarn a terrifying appearance and a nauseating smell.
Bereskarn are encountered several times in Dragon Age: Origins. They use the same skills as great bears, but have much higher stats, with increased armor, health, attack and defense.
During the Magi Origin quest The Harrowing, the Warden encounters a sloth demon in the form of a bereskarn who offers to teach Mouse to shapeshift if the Warden can answer three riddles or defeat it in battle.