A wraith is a type of paranormal being, a product of the Magick Realm.
In the files of the Ministry of Occultism is a document labeled Liches and Wraiths describing supernatural creatures:
Wraiths are typically the servants of Liches. Their souls are placed in a small part of their master's soul artifact, making them controllable. Unlike Liches, however, wraiths generally lack physical bodies and manifest only non-corporeally. On instruction they can possess living humans and apply a certain amount of influence to their environment. The closer the Wraith's Mind is to its Soul, the more control it had, but as the space widens the more wild and unfocused its influence becomes.