Possibly trapped souls, possibly 'echoes of the aura', ghosts are the restless dead still kicking around on earth. Oftentimes they are more frequent if the person died a violent death or if there is strong preternatural force involved with their death or in the area after their death.
Generally, a ghost will not stray far from where it died or where its mortal remains are buried, nor can it do much other than create a very slightly cold spot and perhaps make faint whispering, dim shadowy images, and a slight creep up the spine in the dark of night. If a person pays attention to these slight hints (for more than two or three poses), the ghost can upgrade to a more humanoid form with a faint glow, the occasional speaking-level phrase, and a rather notable 'pins and needles' sensation. If still acknowledged, soon the form is quite identifiable as a stylized form of the dead person who can speak normally and manipulate objects to a very slight degree (candles may flicker, hair brushed about, but nothing actually moved that is more stable than dust, hair, or paper). This trend can increase with the continued acknowledgment of the ghost's presence, up to full-on poltergeist effects. The ghost can also stray from its haunt as long as someone is sustaining it.
Animators performing Zombie Raisings in the area tend to make ghosts manifest at a faster rate, as do Necromancers who aren't even doing anything to make the ghosts act up. No matter how they manifested, a ghost's abilities will start to fade once folks leave the area or start to ignore them (which can be very tricky if they're manifested enough).
Oftentimes, ghosts are just "echoes" of their living selves, not really able to think new thoughts or deviate from previous behaviour. These echoes often seem to have large quantities of limestone, marble, or quartz nearby (possibly having to do with a recorded piezoelectric pattern, and possibly the reasoning behind those minerals being popular for gravestones). Rare is the ghost that is the person "living on beyond death" like a vampire or a particularly well revived zombie.
Due to all this, ghosts can not be player characters (but folks can attempt to RP them as NPCs if they do so with caution and self-restraint).
