Undead and Necromancy
Animated dead are a supernatural evil force, and can be sensed via the Detect Evil spell.
The main way to create animated dead is via the spell Animate Dead, which uses shadows summoned into the vessels of skeletons and dead bodies to create the dead. In most situations, the inhabiting shadow loses much of its abilities and intelligence during the process of being forced/summoned into this world and fused with dead remains.
When using Create Undead the shadows maintain some of their power, resulting in more free-willed creations than the Animate Dead spell.