Some skeletons are animated through necromancy. Most skeletons are raised from battlefields and thus are often seen still clothed in rotting garments and rusting armor. Some skeletons still fight with the weapons they died clutching. Others, specifically created only by the most advanced necromancers are able to cast magical spells. Whatever they attack with skeletons are basically mindless automatons who are either directly controlled, or made to follow a specific order from their creator. If sufficiently damaged, the magic holding their bones together will dissipate, and they will crumple lifelessly to the ground.

Some skeletons, however, actually seems to possess some kind of intelligence, like Mordresh Fire Eye, found in Razorfen Downs. He can be seen talking to and encouraging his brethren, holding a speech about how the undead Scourge will consume the whole of Kalimdor.

In addition to the skeletons described here, some others may be other types of undead that are simply very old and all their flesh has rotted away, leaving nothing but bones.