There are some NPCs that appear as mostly transparent apparitions, instead of the normal solid appearance. These fall into four main categories.
Spirits are the most common type of spectral NPC. These are usually dead NPCs who have returned as apparitions, although some are NPCs who were magically trapped in either an inanimate object or some type of creature. They differ from Ghosts as they still retain their unique appearance, while ghosts have a generic appearance.
For more information, see the Spirit page.
Shadows are apparitions created through use of Shadow Magic. They are very dark spectres with small dots of purple light for eyes, but otherwise they retain the appearance and abilities[verification needed] of the NPC they are based on.
For more information, see the Shadow page
Projections are magically-created apparitions, either as a way to relay a message to someone or as a memorial. Visually, they are similar to spirits.
For more information, see the Projection page