A necromancer needs a way to get real bodies too. Beyond killing those around them, a non-consecrated grave will need to be dug up, and that will cause serious trouble with the local authorities once it is discovered. A useful spell (like the Exhume the Bounty of the Earth) could do the job well as it will likely leave the earth as it was originally.
However I cannot ignore that sometimes digging out a mass of earth is just the right task. The spell below digs out an area of land bigger than a typical grave and could be used to fill it back in too. It could also be a good way to hide a few bodies, or even used as a combat effect.
The Gravedigger’s Pleasure
Rego Terram 5. R: Voice, D: Momentary, T: Individual
The caster excavates soil, sand, mud or any other earthen substance from one place to another, allowing the extraction of all materials into a place and pattern of their choosing. The digging action lifts the earthen material and any items it contains.
As an exceedingly simple task a Finesse skill check of 6+ is needed to exhume an object properly. The spell affects up to ten cubic paces of material.
(Base 3, +2 Voice)
There may also be odd times when the necromancer needs to maintain the illusion that a corpse is able to speak. This effect could be cast spontaneously very easily by almost any Magus, however knowing a formulaic version means subtle casting is so much easier.
Speak Through Silent Lips
Creo Imagonem 5, R: Voice, D: Concentration, T: Individual
Allows the caster to create a speaking voice of their choosing within range and control what it says. The caster is not required to speak each word conjured by the illusion but must maintain concentration.
(Base 1, +2 voice, +1 Conc, +1 intelligible speech)
Lastly a version of the popular anti-rotting spell for animal corpses. A necromancer who works with animal bodies might not be viewed with quite the same degree of disdain? Nah, still creepy. Animal corpses will be easier to come by.
Circle Against Putrefaction of Beasts
Creo Animal 5, R: Touch, D: Ring, T: Circle
The animal materials within the target circle remain fresh, and are protected from rotting and purification.
(Base 2, +1 Touch, +2 Ring)
Charm Against Putrefaction of Beasts
Creo Animal 10, R: Touch, D: Moon, T: Individual
The targeted animal materials remain fresh, and are protected from rotting and purification.
(Base 2, +1 Touch, +3 Moon)
I also though of a macabre spell which are unlikely to be ever used, but suits a strange mood that pondering necromancy puts me in. When you have Necromancy as your hammer, everything looks like a corpse shaped nail. A horrible way to ford for a river, a rain to disrupt attackers, or a way to bury an opponent.
Rain of One Hundred Corpses
Creo Corpus 35, R: Voice, D: Diameter, T: Group
This spell causes one hundred corpses to fall from the sky and blanket an area within range chosen by the caster. Each corpse is identical and size +1.
(Base 5, +2 Voice, +1 Diam, +2 Group, +1 size)
Sculpting dead flesh isn’t in the Hermetic magic guidelines however I took the Terram base 2 and decided that it was one degree more difficult and creepy.
Sculpt Unhallowed Flesh as Clay
Muto Corpus 15, R: Touch, D: Sun, T: Part
This spell changes the consistency of dead human body material to that of soft clay which can be shaped. The spell can affect an entire corpse or a smaller segment.
(Base 3, +1 Touch, +2 Sun, +1 Part)
And once the Ars Magica necromancer realises that they can work with flesh and bodies as a resource, complex items can be prepared.
Construct From Flesh the Unhallowed Tools
Rego Corpus / Muto 15, R: Touch, D: Momentary, T: Group
This spell transforms a corpse or corpus based materials into a item of equipment required by the caster, akin to how a craftsman would create an item. This requires a Finesse roll to successfully construct an item (see Covenants p.51), and may be modified by an appropriate skill.
(Base 3, +1 Touch, +2 Group, +1 flexibility in outcome)
For these and over 250 other new Ars Magics spells see the list of spells.