Spirit. It cannot be broken and it cannot be stolen away. A victim in the throes of despair might feel otherwise, and certainly the victim‘s “master” would like to believe it so. But in truth, the spirit remains, sometimes buried but never fully removed.
In the overworld, far above, animals kill so that they might eat and live. But the creatures that haunt the dark labyrinth beneath the face of Toril do not kill to live, for life itself is agony to them. They kill because they are driven to kill: by madness, by hatred, and by the foul atmosphere of evil that pervades every stone of this place. They kill because, only in killing, can they know release.