Is there a name for a ghost master?

[Spore]

What about Geistergruppenführer? Necromant mit Fahrvergnügen?

You may want to avoid anything with "Führer" in it on an English speaking forum, as fitting as it might be Points for Fahrvergnügen, though.

The slightly funny (?) connotation still stands in German. Though I like "Geisterreiseführer" (ghost tour guide). :D

Ghost Master sounds good to me, I'd accept that.

Geistermeister is probably too much, no?

Verschleierter Ghostomantist

Jokes aside: Spectromancer is probably the shortest thing that makes sense and distinguishes itself from Necromancer.