From Path of the Vampire Wiki
Wraiths are the shades of long-dead vampires, whose spirit forms have been consumed by shadows in the shadow realm. They are often driven insane by the many hundreds of years being stuck in a limbo-state. Although they are different from spirits (the ghosts of human beings, who are sometimes dragged into the shadow realm), they still spectral in nature, and are mostly unable to manipulate physical objects. However, unlike spirits, they often retain certain abilities.
Wraiths can best be described as translucent shadows. Their forms are featureless, just as any silhouette would be. However, wraiths, while in the world of the living, are able to go invisible at will, and so most never see one unless the wraith wishes it. While in the shadow realm, all wraiths are visible.
The power of a wraith varies from subject to subject, depending on the will of the individual, the age of the vampire, and the length of time they have spent dead.
Wraiths in the shadow realm are all able to drain anima from other spirits or wraiths. Some wraiths in the shadow realm are also able to use certain powers (mostly telepathic or allurist), even many years after their death. Although a dead vampire will slowly lose their power over time, some have been said to find ways to thrive on feeding on the souls of weaker spirits without ever losing their sanity or willpower.
Wraiths cannot return to life, except for those that died in the area surrounding Harper Rock. Some can, however, return to the real world as wraiths, if they are summoned, or if they are particularly powerful. A good example of this is the guide wraiths who are often sighted in Harper Rock. They perished in various distant lands, and so they are unable to return as vampires, but they have found a way to cross the barrier between realms and haunt the mortal world as a spirit creature. Wraiths can also be summoned from the shadow realm, without actually returning to life, as such. It is speculated that some vampire spirits have been too badly corrupted by the shadow realm to return to life as a vampire, even if they are summoned.
While in the real world, wraiths have the ability to pass through solid objects, turn invisible, drain anima from living beings and speak to people.
Master Wraiths AKA "Guides"
There are a number of wraith guides who have appeared in Harper Rock who claim to be ancient masters, from far away lands. They seem able to project their spirits to Harper Rock, even though they died far away, or many hundreds of years ago.
They appear and communicate with vampires, offering to teach them how to master their talents. In return, they ask for a sacrifice of vital energy. It is the opinion of many that these wraiths are aware of the rip in the barrier between worlds, and are seeking to grow in sufficient power to return to life themselves.