There is nowhere said that it uses necromancy. Fear effect is because you believe something(illusion which is what this spell does) to be true, not from spell itself.Phantasmal Killer
Illusion (Phantasm) [Fear, Mind-Affecting]
Level: Sor/Wiz 4
Components: V, S
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Target: One living creature
Saving Throw: Will disbelief (if interacted with), then Fortitude partial; see text
Spell Resistance: Yes
You create a phantasmal image of the most fearsome creature imaginable to the subject simply by forming the fears of the subject’s subconscious mind into something that its conscious mind can visualize: this most horrible beast. Only the spell’s subject can see the phantasmal killer. You see only a vague shape. The target first gets a Will save to recognize the image as unreal. If that save fails, the phantasm touches the subject, and the subject must succeed on a Fortitude save or die from fear. Even if the Fortitude save is successful, the subject takes 3d6 points of damage.
If the subject of a phantasmal killer attack succeeds in disbelieving and is wearing a helm of telepathy, the beast can be turned upon you. You must then disbelieve it or become subject to its deadly fear attack.