A wraith? It can be done, but that really is out of the norm for the RP. Most other characters are living. It's hard to tell how a wraith would fit in. Especially since most characters wouldn't be too friendly to the undead. A necromancer is one thing, but a wraith would likely be attacked on sight.
I see. You can play him, but this will make things harder for him. Just giving you fair warning. It would be out of character for my characters and those of the other players to accept a wraith as an ally without some serious reasons.
That's fine. Might I make a suggestion? He can show up at the house of an archmage, a character of mine named Ophion. He (and his wife Aurescia) are unlikely to be as hostile to a wraith as other characters would be.
Or, if you want him to be resurrected at some point, he can visit the priest Vespion. What species was he in life? I know it is possible he might have forgotten that.
I'm fine with him being undead. He can't remember ever being anything else. He was once a powerful dark elf, who turned to necromancy for self preservation. He is in disguise as a elf worker, so others don't reject him.