Shades are half-real spirits, doomed to wander Xanth until its misdoings are corrected.
Ghosts, spirits, the unquiet dead; Shades have several common nicknames but in the end, they are considered evil. Shades are formed after someone does something wrong in life, or something truly evil. They can be doomed to wander the shadows and nights trying to correct their mistakes. Many are bound to the area where they died.
Shades posed no real threat to ordinary people most of the time. They can't go out in the day or enter a lit area and they can't enter populated areas. Where most people run into shades is when they unwittingly decide to rest near where a shade lives. A shade can inhabit a living body. This process takes about one hour, and can provide the shade an opportunity to escape its situation. However, due to their slower speed, all a person needs to do is get up and walk away and they can escape the shade. This is called "pulling the shade".
If a shade performs a task that rights what went wrong it its prior life, its burden can be lifted and it may rest in peace.
- A Spell for Chameleon, Chapter 3