An interesting idea would be to make a necromantic Criamon from the Path of Seeming with:
Puissant Enigmatic Wisdom
Minor Focus: Ghosts
Inscription of the Soul
Other virtues to taste
The Path eventually gives Second Sight and Magic Sensitivity.
Spirit Familiar also has unique benifits for a ghost-oriented necromancer.
Inscription of the Soul allows the magus to 1.) Use his magic focus to instill powerful effects into his "ghost" talisman and his ghost familar and 2.) Use normal ranges when he "Passes through Seeming" (i.e. sends his ghost out wandering.)
Clear Thinker and Keen Vision (which also improves Second Sight rolls) also help when dealing with confusing ghosts, or devious demons.
Enigmatic Wisdom helps unravel the reasons for a ghost lingering on.
Also interesting story possibilities.
This magus believes that the restless dead offer unique insights into the Enigma. They lie on the threshold of eternal rest in harmony and the strife of the world, torn beings on the metaphysical edge of time and being.
Moreover, like the Donatores, he believes that it is a sacred duty to help the restless dead find their repose. He is Driven to aid the dead resolve their unsettled affairs.
Finally, he is gifted at questioning the dead to unravel greater mysteries entirely. He delights in investigating long-abandonned temples and tombs which are often, he believes, sites of great, unresolved frustrations of the long dead.
To this end he may have the Gentle Gift, to facilitate investigations amongst mundanes, or (my preference) a secondary specialty in imaginem and a strong array of mentem spells to allow him to operate from the shadows. The Thousand Unexpected Pages power, which allows him to peer into the past of inanimate objects, aids in his investigations and helps him to find Arcane Connections.
Probably the most gifted ghost-oriented necromancer alive, he believes that it is apt to summon the dead to help unravel the vexilations of the living. Several of the ghosts indebted to his aid have agreed to linger on a short while longer, to aid his continued ventures.