Lucifer Faustus gives a ritual to use them without any further explanation in his Abaddon book.
Outside of gaming, no, but the arak has a very rich and varied ecosystem including vamipic entities, parasites and egregoric beings created from rpg and gaming mental spaces it could be anything or a few of these.
I wouldn’t really expect a lot of ability from such things though, maybe in enormous numbers?
I would meditate on the link you have through the book to the suthors local astral and see if you can call to you an example to study, and ask it about itself.
A wraith that runs on blood, yes.
Could you tell me where to read more on the subject, please.
Wraiths are a type of Scottish spirit. You don’t hear much about them these days, but Marvel picked them up to use in their storylines. They were generally believed to be created when magic went wrong, usually magic involving time or immortality. They are soulless and live off human rage and fear. It may just be another name for common astral parasites.
You can easily google them to find a wealth of information, but I would skip over the gaming and comic book sites if you want the real stuff.