Ghosts, also called Shades, are supernatural entities formed by the psychic footprints of people who are dead as opposed to lingering souls. Ghosts are found in: Grave Peril, Dead Beat, and Ghost Story.
The most dangerous ghosts are very substantial and appear to be human feeling real emotion. A shade with a greater sense of self or purpose can maintain its individuality and state of mind. (ref?)
They do not play by the rules of reality, and they cannot be affected by someone whose presence they do not acknowledge. Most ghosts dwell at the very edges between the Nevernever and the mortal realm, though they can cross over to the mortal realm with relative ease at graveyards and sites of importance during their lives or during Halloween. (ref?) Faith magic works best against spirits.  The Fae can also interact with them. Ghosts are drawn to the magically gifted.  Ghosts may also be summoned by ectomancers in order to contact their loved ones, or to gather information.(ref?)
As already mentioned, not all ghosts are of equal power. Weaker shades may just have phantom-like forms, while others may be more defined and substantial. More powerful ghosts may interact with the mortal realm more actively than weaker ghosts. Agatha Hagglethorn was able to turn off the power in an entire ward at a hospital, enchanting the entire floor into a sleep, as well as using her spirit-self to suffocate babies. 
They can also teleport or possess inanimate objects. The presence of a strong ghost can make the flame on a candle burn "pinpoint-clear".
Ghosts cannot roam the mortal world between sunrise and sunset, nor can they wander on holy ground. (ref?) The only way a ghost can manifest is if it is insane.
Ghosts are also vulnerable to what Harry calls 'ghost dust', both in and out of the Nevernever. They can be trapped in a circle and then harmed by fire, or blocked by thresholds. When wounded, they bleed ectoplasm.
Ghosts can be sensed by priests, shamans, and people who care for the souls of others.. They can also be sensed by dogs, about one in ten can, and cats, who are not very impressed by them.
Types of ghosts Edit
Becoming a wraith Edit
- Main article: Wraith
All shades who can't maintain a purpose or lose too many memories and their self-reason become Wraiths, who devour the memories, the life, of other shades.
They are described as a humanoid, gray form, that lacked features, gaping, sunken holes for eyes, empty mouths, and nearly skull-like. They have a cold presence.
Becoming a lemur Edit
- Main article: Lemur
Shades who go against Providence and give themselves over to rage and malice, they are dressed in dark robes and know no pity, restraint, or fear.
Specters are semi-corporeal Ghosts.
Corpsetaker called up a number of Specters to attack Grevane's Zombies outside Harry Dresden's apartment. According to Mab, "Specters most potent" that are "beyond the beck of the mortal pale, will rise up to the night and the stars at the sound of his horn, and join the Hunt. ", Harry translates: "So, a gaggle of wizards who stock-in-trade is enslaving the dead to their will is interested in a being (Erlking) whose presence calls up powerful spirits they couldn't otherwise reach."
Near the site where the Darkhallow is being performed, hundreds of specters rose up out of the ground where Harry, Butters, and the Wardens were. Butters empowers a circle and kept up a steady beat for Sue. Kowalski was killed by specters when they rose up out of the floor underneath him, he didn't have a chance. In Ghost Story, the insane serial-killer ghosts can manifest and were dubbed: "Lecter Specters".
There are groups of ghosts that more or less act together for their own reasons.
Sir Stuart's Ghost-SoldiersEdit
They are guardian spirits or protecter spirits of Morty's house and are more than spirit soldiers. They were "ghosts of duty and obligation unfulfilled, had remained behind to see their task to completions." They were shades of faith, love and duty. The served as a balancing energy with the dark power for the killer ghosts.(ref?)
They were wispier and foggier, less defined and were the size of a mob. The ghost army soldiers ware all from Different eras: Revolutionary War, buckskin woodsmen, trappers, Native Americans from wars proceeding that one, farmers from the Civil War, shopkeepers from the turn of the century, men in suits, some with shotguns or tommy guns, doughboys from WWI, Buffalo Soldiers, gun-toting cowboys, and Vietnam War grunts.
They aid Lindquist out of friendship and respect rather than compulsion. They had become faded over time from loss of too many memories, forgetting their mortal lives little by lithe. They are sane, so they can not manifest, nor they could stop Boz from killing Lindquist. 
The Lecter Specters Edit
All the ghosts watching Mortimer Lindquist’s house as it burned were killers, Mort gave them a home, a reason to turn aside their madness. With Mortimer gone, they will kill again. According to Sir Stuart, ”fifty years of maddened shades unleashed upon the city all at once. Preying on mortals. Blood will run in buckets.” Harry told Murphy that if they don't get Mortimer back, that they manifest making them real like the Nightmare.
Harry dubs them the insane killer ghosts the Lecter Specters. Since they are insane, they can manifest—sane ghosts don't interact with the mortal world. There were some famous Chicago serial killers amongst them.
The Lecters answered Harry's call to come home at Morty's house, along with the Ghost-soldiers, and follow him to rescue Mortimer. They fought Evil Bob's forces in the Nevernever and fought the Lemurs and Big Hoods in the hideout. Corpsetaker ate them, like the Darkhallow. She did that to gain enough madness to manifest and some of her powers back with the ability to steal any body.
The Wolfwaffen were a part of the Evil Bob's defenses of Corpsetaker's stronghold from the Nevernever side. They wore the bland-and-gray uniforms of the old Waffen-SS. Their faces were distorted into the jaws and muzzle of a wolf but bearing no fur. Their eyes were black empty holes—there were no eyes, just sockets. There were machine-gun crews, rifle men—"riflethings". They looked hungry to spill blood, or rather ectoplasm.
- Ron Carmichael
- Harry Dresden
- Eternal Silence
- Grey Ghost
- Agatha Hagglethorn
- Collin Murphy
- Sir Stuart Winchester
In the seriesEdit
- Main article: Grave Peril
- Main article: Dead Beat
- Main article: Ghost Story
Father Forthill sensed the chill of Harry's Ghost when he neared him. Sir Stuart said that he must be one of the "good ones": minister, priest, shamans, whatever. Spending your life caring for souls tends to give them the ability to sense spirits, though not exactly soul, ghost aren't that much different. 
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Grave Peril, ch. 2, page 12. Paperback, 2003.
- ↑ Ghost Story, ch. 3
- ↑ Grave Peril, ch. 3
- ↑ Ghost Story, ch. 22
- ↑ Grave Peril, ch. 4
- ↑ Butcher, Jim. "Grave Peril", Chapter two, paperback, 2003.
- ↑ Ghost Story, ch. 6
- ↑ Grave Peril, ch. 5
- ↑ Ghost Story, ch. 5
- ↑ 10.0 10.1 10.2 Ghost Story, ch. 9
- ↑ 11.0 11.1 11.2 Ghost Story, ch. 3
- ↑ 12.0 12.1 12.2 12.3 Ghost Story, ch. 5
- ↑ 13.0 13.1 Grave Peril, ch. 21
- ↑ 14.0 14.1 14.2 Dead Beat, ch. 21
- ↑ 15.0 15.1 Dead Beat, ch. 23
- ↑ 16.0 16.1 16.2 16.3 Dead Beat, ch. 32
- ↑ 17.0 17.1 17.2 Dead Beat, ch. 39
- ↑ Ghost Story, ch. 3 and 5
- ↑ Dead Beat, ch. 41
- ↑ 20.0 20.1 20.2 20.3 Ghost Story, ch. 47
- ↑ 21.0 21.1 Ghost Story, ch. 43
- ↑ 22.0 22.1 22.2 Ghost Story, ch. 40
- ↑ Ghost Story, ch. 2
- ↑ 24.0 24.1 24.2 Ghost Story, ch. 15
- ↑ Ghost Story, ch. 41
- ↑ Ghost Story, ch. 41–45
- ↑ Ghost Story, ch. 46
- ↑ Ghost Story, ch. 9