The Path of Bones

Necromancy

1) Tremens
Tremens allows the necromancer to make the flesh of a corpse shift once. An arm might suddenly flop forward, a cadaver might sit up, or dead eyes might abruptly open. Needless to say, this sort of thing tends to have an impressive impact on people who aren't expecting a departed relative to roll over in his coffin.
System: To use Tremens, the necromancer spends a single blood point, and the player must succeed on a Dexterity + Occult roll (difficulty 6). The more successes achieved, the more complicated an action can be inculcated into the corpse. One success allows for and instantaneous movement, such as a twitch, while five successes allows the vampire to set up specific conditions under which the body animates ("The next time someone enters the room, I want the corpse to sit up and open its eyes"). Under no circumstances can Tremen cause a body to attack or cause damage.

2) Apprentice's Broom
With Apprentice's Broom, the necromancer can make a dead body rise and preform a simple function. For example, the corpse could be set to carrying heavy objects, digging, or just shambling from place to place. The cadavers thus animated do not attack or defend themselves if interfered with, but instead attempt to carry out their given instructions until such time as they've been rendered inanimate. Generally it takes dismemberment, flame, or something similar to destroy a corpse animates in this way.
System: A roll of Wits + Occult (Difficulty 7) and the expenditure of a point of both blood and Willpower are all that is necessary to animate corpses with Apprentice's Broom. The number of corpses animated is equal to the number of successes achieved. The necromancer must then state the task to which he is setting the zombies. The cadavers turn themselves to their work until they finish the job (at which point the collapse) or something (including time) destroys them.
Bodies energized by this power continues to decay, albeit at a much slower rate than normal.

3 Shambling Hordes
Shambling Hordes creates exactly what you think it might: reanimated corpses with the ability to attack, albeit neither very well or very quickly. Once primed by this power, the corpses wait -- for years, if necessary -- to fulfill the command given them. The orders might be to protect a certain site or simply to attack immediately, but they will be carried out until every last one of the decomposing monsters are destroyed.
System: The player invests a point of Willpower, then spends a point of blood for each corpse the necromancer animates. The player must succeed on a Wits + Occult roll (difficulty 8); each success allows the vampire to raise another corpse from the grave. Each zombie (for lack of a better term) can follow one simple instruction, such as, "Stay here and guard this graveyard against any intruders." or "Kill them!"
Note: Zombies created by Shambling Hordes will wait forever if need be to fulfill their function. Long after the flesh has rotted of the mystically animated bones, the zombies will wait...and wait...and wait -- still able to preform their duties.

4) Soul Stealing
This power affects the living, not the dead. It does, however, temporarily turn a living soul into a sort of wraith, as it allows a necromancer to strip a soul from a living -- or vampiric -- body. A mortal exiled from his body by this power, becomes a wraith with a single tie to the real world: his now-empty body.
System: The player spends a point of Willpower and then makes a contested Willpower roll against the intended victim (difficulty 6). Successes indicate the number of hours during which the original soul is forced out of its housing. The body itself remains astronomically alive but catatonic.
This power can be used to create suitable hosts for Daemonic Possession.

5) Demonic Possession
Daemonic Possession lets a vampire insert a soul into a freshly dead body and inhabit it for the duration. This does not turn the reanimated corpse into anything other than a reanimated corpse,and one that will irrevocably decay after a week, but it does give either a wraith or a free-floating soul (say, that of a vampire using Psychic Projection) a temporary home in the physical world.
System: The body in question must be no more than 30 minutes dead, and the new tenant must agree to inhabit it -- a ghost or astral form cannot be forced into a new shell. Of course, most ghosts would gladly seize the opportunity, but that is a different matter. Should the vampire, for whatever reason, wish to insert a soul into another vampire's corpse (before it crumbles to ash), the necromancer must achieve five successes on a resisted Willpower roll against the original owner of the body. Otherwise the interloper is denied entrance.
Note: The soul can use whatever physical abilities (Dodge, Brawl, Potence) his new home possesses, and whatever mental abilities (Computers, Law Presence) he possesses in his current existence. He cannot use the physical abilities of his old form or the mental abilities of his new one.