Phantom

A phantom is another term for an undead spirit or ghostly image.

Types of phantoms
Recently, Karazhan has reawakened — an evil presence has taken the tower as its own, its halls crawling with spirits.
 * Many visions are seen at Karazhan in the book The Last Guardian (they are described as phantoms, as well as; time-lost visions, timelost wraiths, ghosts, ghosts of the past, specters, and illusions). These visions were said not to be capable of causing physical or magical harm.
 * Revenants — phantom creatures that live only to rage and use their powers for destruction.
 * Phantom image — One of the blademasters’ more mystical abilities is to create duplicate phantom images of themselves. Though the phantom images can move about freely of their own volition, they are not true entities unto themselves.
 * Vengeful Phantom — Stratholme
 * Wrath Phantom — Stratholme
 * Spiteful Phantom — Stratholme
 * Phantom Attendant — Karazhan
 * Phantom Guardsman — Karazhan
 * Phantom Guest — Karazhan
 * Phantom Hound — Karazhan
 * Phantom Stagehand — Karazhan
 * Phantom Valet — Karazhan
 * Phantom Boar
 * Phantom Crew
 * Phantom Executioner
 * Phantom Hallucination
 * Phantom Leotheras
 * Phantom Mage
 * Phantom Officer
 * Phantom Pearltusk
 * Phantom Pearltusk Calf
 * Phantom Swordsman

In World of Warcraft
World of Warcraft has several phantoms, but mostly in Karazhan and Stratholme.

In the RPG
A phantom weapon appears translucent and occasionally fades partially into non-existence, allowing it to sometimes penetrate armor with great ease.