The Ars Magica Hermetic Projects sourcebook contains a robust section which deals with aspects of Living Corpses, Necromancy, and details of binding ghosts (p96-118). Many of the more flamboyant spells that a Magus might develop later in their necromantic career are present in this book; so much so that repeating material here would be basically copying it. Hermetic Projects is one of the best Ars Magica books for deep investigation into how wizards might advance special interests.
Amongst other “creepy and dead” things it covers huge animations of human corpses, animating zombie armies of many sizes, conjuring human corpses in large numbers, and the creation of permanent quasi-sentient undead animals and humans. It is great material to aspire to.
Aside from that material which I was going to post variations for, here are a few ancillary spells which may be useful for Ars Magica Necromancers.
There is a fair rationale for an experimenting necromancer to use Ring and Circle version of these spells for their investigations. A set of niche effects, but perhaps worthy for devices within the necromancer’s lab.
Circle to Conjure the Remains of Man
Creo Corpus 20, R: Touch, D: Ring, T: Individual
This spell creates a corpse of up to size +1, with an appearance subject to the desires of the caster. Matching to a specific individual is possible with a successful Finesse check of 12+, with an optional familiarity adjustment between +/-3 depending on how well the caster knows the subject.
(Base 5, +1 Touch, +2 Ring)
Circle of Walking Servants
Rego Corpus Mentem 25, R: Touch, D: Ring, T: Circle
Turns all corpses in the circle into a nearly mindless servants that can follow your simple verbal commands faithfully but unimaginatively. Unless the corpses are preserved with Charm Against Putrefaction or the equivalent, the bodies will decay normally, but even a skeleton can be animated.
(Base 10, +1 Touch, +2 Ring, Mentem req free)
Circle Against the Putrefaction of Man
Creo Corpus 5, R: Touch, D: Ring, T: Circle
The human materials within the target circle remain fresh, and are protected from rotting and purification.
(Base 2, +1 Touch, +2 Ring)
All these zombies are dangerous if there isn’t a way to deal with them (especially those not in circles). A typical undead ignores fatigue penalties and may also ignore some wound penalties depending on how the damage is inflicted. It would be very difficult to use pain as an attack on an animated foe. Dust to Dust (PeCo15) is the core rulebook spell for destroying a corpse and it is very effective on animated dead.
A variant to ensure a necromancer never gets the drop on a magus might be crafted to destroy both animal and human corpses and also to destroy a group of targets.
Dust the Unwanted Remains
Perdo Corpus / Animal 30, R: Voice, D: Momentary, T: Group
This spell destroys a selection of human and animal corpses, up to 10 size +1 corpses which are not controlled by an independent spirit.
(Base 5, +2 Voice, +2 Group, +1 Animal corpses)
As a level 30 effect it is significant to learn however most animated dead do not have any magical resistance so it is likely to be effective.
These effects, like all the others I’ve pondered are part of a new spells compendium for Ars Magica.