Necromancy is a very toolboxy discipline, including 22 cards allowing for many effects ; not all the cards are worth being played, though, and some will be useful only in some very precise context. Comments (updated as of K:MW) by Orpheus.
Note : the cost of the cards can be reduced by one for Giovanni if the Path of Bone is in play, and all your Necromancy Actions will give you 1 Pool if you have the Tower of London in play ; not to mention the Charisma or Regina for Necromantic allies, so some apparently expensive cards can easily be made more affordable in a well-thought deck...
As there are now many minions with inf Nec, I gave different ratings to inferior and superior versions of these cards, for easier browsing / deckbuilding. When the card is good at either version (although usually a little less at inf, of course) there may be only one rating.

Card Text
Baleful Doll
Unique equipment. [nec] Choose a vampire controlled by your prey. The bearer may tap himself or herself and burn the Baleful Doll during his or her untap phase to cause the chosen vampire to burn 3 blood. [NEC] As above, but choose a vampire controlled by any Methuselah.
An interesting equipment, although really interesting only in a dedicated deck and needing some setup. Ideally used with cards like Society of Leopold. And of course, diminishing blood ressources is always good. Too bad it's Unique !
Breath of Thanatos
Combat/Action Modifier. [nec] +2 stealth. Only usable on an action to employ or recruit a wraith. [NEC] Strike: 1 aggravated damage.

What can I say ? The inferior, while cornercase, can be useful in some decks ; the superior seems better for the Harbingers (block, soak with For and surprise strike) than the Giovanni (who will probably Grapple). It is less good than Claws, as it constitutes a strike. Still, something new and potentially useful.
Call of the Hungry Dead
Only usable when a minion is attempting to block. [nec] The blocking minion gets -1 intercept. [NEC] This acting vampire burns 1 blood to cause the block to fail. The blocking minion cannot attempt to block this action again.

One of the staple Necro cards since Final Nights ! In conjonction with Seduction (and Crocodile's Tongue ?) it gave birth to the Giovanni "Responsible Bleed", a winning strategy especially now, with all those Aus walls...

Chill of Oblivion
+1 stealth action. [nec] Put this card on a ready vampire. This vampire may burn this card in combat to treat aggravated damage as normal for the remainder of combat. A vampire can have only one Chill of Oblivion. [NEC] As above, and this acting vampire untaps during your next discard phase.
So, will this card change everything for the fighting Necromancers ? It allows them to endure aggropocks, to make some bruise'n'bleed by daylight... Not as great as it first seemed in my opinion, but an interesting card overall.
Combo with Ex Nihilo, Dawn Operation, Domain of Evernight.
Compel the Spirit
+1 stealth action. Only usable if a retainer or ally you control has been burned since your last turn. [nec] Move the card from your ash heap to your hand. [NEC] Move the card from your ash heap to your ready region, even if this vampire doesn't meet the requirements, if any, of the card (use the normal version if it requires a Discipline). Move X life counters from the blood bank to the card, where X is the number of life printed on the card. If a retainer is chosen, it must be placed on the acting minion.
Incredibly efficient card, but very specialized
since it will find a place only in an ally deck type. Before Bloodlines, Necromancy was the only discipline providing such a resurrection trick. Once again, the superior version is clearly more powerful since it allows you to save one recruit/emply action and some pool or blood.
Daemonic Possession
[nec] Only usable when a minion controlled by another Methuselah has been burned since your last turn. Move that minion from his owner's ash heap to your ready region, put 1 blood or life from the blood bank on the minion and tap the minion. You now control the minion. [NEC] As above, but the minion is untapped.

My advice is very different from what we originally said :
It can be great to raise our enemies back from the dead. But this card is at 0 stealth, costs 2, and has a very limited time window. This is only a half-problem when you can get the card back from the ash heap when needed, but still... Worst of all : the Giovanni have access to Graverobbing, which is much better for an offensive deck (no need to burn the minion...). I'd keep Daemonic for specific purposes, or for en environment where vampires get burned regularly.

Dead Hand
Combat. [nec] Strike: make a hand strike at +1 damage. [NEC] As above, and the damage from this strike cannot be prevented by cards that requires Fortitude.
Yeeeeeeah !! At last a true combat card in Nec !! Usable under Grapple, it makes the Giovanni potentially feared fighters. Strangely, it would be great with the G4 For Giovanni, but most of them have inferior Nec, and this card is clearly meant to be used at sup (at least for Potence clans). At inf, it can give some punch to Matthias... Combo : Torn Signpost / Immortal Grapple, Claws of the Dead...
Death Pact
This card is an action card that becomes a retainer card. +1 stealth action. [nec] (D) Put this card on a ready vampire. If that vampire is burned, put this card on the vampire who brought this card into play. This card then represents a -wraith- retainer with 2 life. Once each combat, the vampire with this retainer may change one damage from aggravated to normal. [NEC] As above, but the retainer has 3 life.
One of the worst cards provided by necromancy. Not only is it difficult to transform it to an actual retainer (burning a vamp is not always easy), but the result is inferior to a mere flack jacket. If only it could *prevent* aggravated damage instead. But no, it changes aggravated to normal damage. Can in some particular cases be useful in a Thau Giovanni deck, with Bursts of Sunlight. Might also help an Ex Nihiled vampire, but anyway it's very cornercase. Combo with : Julius, March Halcyon, Ex Nihilo.
Divine Sign
+1 stealth action. [nec] (D) Choose a minion. Put this card on this acting minion and untap the acting minion. This minion gets +2 intercept when attempting to block the chosen minion. That minion may burn this card as an action. A minion may have only one Divine Sign. [NEC] As above, and the chosen minion's controller plays with an open hand in the resulting combat if this minion successfully blocks that minion.

Are the Necromancers tending towards the blocking edge ? It sure looks like it ! In combo with Spectral Divination, Masquers or Friend of Mine, it can allow the Giovanni or Samedi to block, and can even be a nice bonus for Aus Necromancers. It can be burnt, so you'd better pack other intercept sources. The untap part makes it not-so-bad if you fail. Will this sign be worth following ? Time will tell...

Ex Nihilo
+1 stealth action. [nec] Put this card on this vampire. The vampire with this card gets +1 stealth. Damage inflicted by this vampire in combat is reduced to 0, and this vampire is immune to non-aggravated damage. This vampire cannot gain blood; any blood this vampire gains goes to the blood bank instead. During your master phase, this vampire burns 1 blood or is burned. You may choose to burn this card during your untap phase. [NEC] As above, but you may burn this card during any Methuselah's untap phase.
A somewhat mitigated result for a promising card at first
sight.The +1 stealth effect is always useful, but the problem of losing blood with no option to gain some is a big handicap. Despite the Weather Control text change which shut down a powercheese combo, Ex Nihilo + Weather Control + Trap which can still be deadly. Combo : Chill of Oblivion, lots of Zombies.
Eyes of the Dead
Only usable when a reacting vampire you control attempts to block a vampire who is attempting to diablerize one of your vampires. [nec] This reacting vampire gets +1 intercept. [NEC] As above, but with +2 intercept.
No need to comment on this card as it is broken to
the bones. It's so powerful it has been banned from tournament. Some say it wallpaperizes Return to Innocence. Just kidding. If it was +1 / +2 intercept against an action targetting one of your torporized vampires, it could help you to stop those graverobbings or rescue famous vamp actions. Or if it was untap + intercept à la 2nd tradition. Or if. whatever, destined for the trashbin
Friend of Mine
Reaction. Requires a ready anarch. [for] Reduce a bleed against you by 2. [nec] +1 intercept. [obt] Only usable when a vampire successfully bleeds you. The acting vampire burns 2 blood.
Not the best of reasons to go Anarchs if you're Giovanni, Nagaraja or Harbinger (they use For but also Aus...) ; could be really useful for the Samedi, though, as they can either try to block or reduce a bleed ! And one more Intercept in any Anarch Necro deck can make a nice surprise... Bart can also use it two ways, although the Obt version leaves me cold.
Gear Up
+1 stealth action. Requires a ready anarch. If successful, untap this anarch. [nec] Move a card from your ash heap to your hand. Discard down to your hand size afterward. [pre] This anarch gets +1 stealth for the remainder of this turn. [vic] This anarch gets +1 strength until your next untap phase.
Without doubt THE reason to play Necro-Anarchs. A Whispers at sup with Inf Nec, and YOU UNTAP !! This card gave me some table wins all by itself. And Stefano, Krassimir, Sarrasine, Raphaela etc. will love the Pre version too.
Grasp the Ghostly
+1 stealth action. [nec] (D) Move a non-unique, non-location equipment from any other Methuselah's ash heap to this minion. Put 3 Pathos counters on that equipment. Burn a Pathos counter during each of your untap phases. Remove the equipment from the game if it has no Pathos counters. [NEC] As above, but the equipment can be unique.
Bring some equipment from the opponent's ash heap,
what a tricky trick ! Yes, but he has to play some equipment - and with the advent of Concealed Weapon, there are fewer chances that weapons will lie in the ash heap due to intercepted equip actions. And even if you find some equipment there, you keep it for a grand total of three turns. Not very useful, it is better to put in an equipment card instead of hoping to fetch a Femur from Grasp the Ghostly.
+1 stealth action. [nec] Put this card on a location you control. The controller of this location can burn this card to cause an action directed at this location to fail. A location can have only one Haunt. [NEC] (D) Burn a location that doesn't require Giovanni to play.
The inferior version is not so interesting, except maybe in
combination with any random powerbase. Note
that your haunted location is still vulnerable to those perfidious votes. At superior, it's a +1 stealth Arson that gets replaced immediately. Combined wih Call of the Hungry Dead, Haunt is great.
Jar the Soul
+1 stealth action. [nec] (D) Tap any ready minion. [NEC] (D) As above, and that minion burns 1 blood.
There are lots of different cards to tap a minion, but
this one is the best. Free, with +1 stealth, and at superior the target burns a blood (which is barely noticeable) Perfect in a weenie dominate deck. Combo : Charnas the Imp, Harass ; also if you can untap after the action and bleed (just try it with Krassimir and some Domain Challenge...).
Lifeless Tongues
+1 stealth action. [nec] (D) Remove a vampire in any Methuselah's ash heap from the game and give this card to that Methuselah. During this acting vampire's untap phase, this acting vampire's controller may look at the hand of the Methuselah with this card. Any minion may burn this card as a +1 stealth action. [NEC] As above, but during any untap phase.
The only Necromancy Rare in K:MW, but certainly not the best. It has a pretty big requirement, and although looking at the hand of your prey can be a great combo with Le Din Tho, it can be burnt. Maybe in combo with the Harbingers Gisela and Anisa, while preparing for the Big Bleed ?
Wraith with 1 life. [nec] Masquer is immune to damage that is not aggravated. The minion with this retainer gets +1 intercept. You may burn this retainer to give any minion +1 intercept. [NEC] As above, with 2 life.
A bit costly, compared to a raven spy, but nearly impossible to kill. Can also be used to give intercept cross table, or emergency auto destruct when someone tries to steal it from you with a Far Mastery. A lot of players would still rather play with a Sport Bike or Mr. Winthrop for the cost. Combo : Weather Control, Shroud Mastery, Compel the Spirit.
Mercy for Seth
[nec] Strike: put this card on the opposing minion. If this minion is a mortal, he or she is burned. During his or her untap phase, the minion with this card takes 1 unpreventable damage. The minion with this card may burn it as a +1 stealth action. [NEC] As above, and this strike inflicts 1 damage as well.
With the other two Nec strikes in K:MW, this one is certainly the worst of the... set ! If you want to burn allies, Release won't restrict you to mortals ; paying one and making an action to inflict one or two damages and forcing an action doesn't strike me as anything near interesting.
[nec] Move any vampire from your ash heap to your uncontrolled region. [NEC] Move a vampire from your ash heap to your ready region and move 1 blood from the blood bank to the vampire..
One of your dead vampires hits the table again ! its often
a decisive action which startles the table. With all those fighters, archons, rushers and so on, one of your vampires will surely be burned for some reason or another. Put him back in the life cycle ;) Useless in inf, this card in sup is known for numerous abuses. Combo : Might of the Camarilla, Bleeding + Daring the Dawn, Soul Gem of Etrius.
Wraith with 1 life. 1 strength, 0 bleed. [nec] The puppeteer can give you control of an ally or a vampire with capacity of less than 5 for the remainder of your turn as a (D) action. [NEC] As above, with 2 life

These cheap but fragile little wraiths are hard to put to good use : 0 bleed, can only block once or twice before dying, can steal weenies which will be tapped most of the time, they can't be transferred equipment from Heidelberg... Using them efficiently will require some setup and a dedicated deck. To bleed they will need equipment or retainers, they could block with guns, Fake Out or maneuvers, Aus could untap small vamps for them and Wormwood could make more for you... Intersting, potentially fun, certainly not dreadsome. Combo : Cloak the Gathering, Shroud Mastery, Psychic Veil, Mask of a Thousand Faces.

Release the Shackled Soul
[nec] (D) Burn an ally or retainer controlled by your prey. [NEC] As above, with +1 stealth.
A very cornercase card since it is limited
to allies and retainers from your prey, even at superior which only grants +1 Stealth. As almost all giovanni master Dominate, common sense suggests to use Far Mastery which steals instead of destroying and has +1 stealth even at inferior. Only the fear of the Orb of Ulain can give it some interest.
Shambling Hordes
Zombie with 3 life. 0 bleed, 0 strength. [nec] When Shambling Hordes enters play, remove an ally or vampire in your ash heap from the game or burn Shambling Hordes. Shambling Hordes gets +1 strength for each life counter it has. Shambling Hordes can never gain life counters; any life counters it gains go to the blood bank instead. Shambling Hordes can enter combat with any ready minion controlled by another Methuselah as a (D) action. [NEC] As above, with 4 life.
Often referred as « The poorman's War Ghoul », this
ally has the best quality for its cost, since you pay its recruitment in blood rather than in pool. This canon fodder horde laughs at Obediences, Taste of Vitae, Terror Frenzy or Drawing Out the Beast. Combo : Trap, Memories of Mortality, Barrens, Pulled Fangs, The Path of Bone, Flack Jacket, Charisma, and Martyr's Resilience (with the Harbingers, Regina, Matthias).
Shroud Mastery
[nec] Usable by a ready vampire when a wraith ally you control is acting. The acting wraith gets +1 stealth. [NEC] Only usable when an action to recruit or employ a wraith is announced. Untap this acting vampire if the action is successful.
A very focused card wich can replace both Freak Drive
and Cloak the Gathering in the right deck. Very good options in Masquer intercept decks. Combo : Masquer, Puppeteers, Brigitte Gebauer, Felix "Fix" Hessian (and to a lesser extent Ambrosius).
Soul Stealing
This card can be played as an action modifier or a combat card. Only usable when a vampire you control burns a vampire controlled by your prey. [nec] This vampire gains an amount of blood equal to half of the burned vampire's capacity (round down). Ignore excess blood. Not usable during combat. [NEC] As above, but usable in combat.
Very difficult to play, this card can at least make you
gain some bonus blood after a savage Decapitate. Curious fact : you can use this card at inferior necromancy after combat if you are the acting vampire. You can play it while reacting or inside combat only of you have superior necromancy. Soul Stealing is rarely seen but has a certain potential. Combo : Anisa Marianna Lopez, Decapitate, Dragon's Breath Rounds.
Spectral Divination
This card can be played as an action modifier card or a reaction card. [nec] +1 stealth. [NEC] +1 intercept.
Excellent card, very versatile despite the blood
cost. This card will find its place in all your Giovanni decks Too bad necromancy only provide one source of stealth and one source of intercept which happen to be the same card. Finds its exact (but free) opposite in Aura Absorption, and both are playble by Bartholomew, Beatrice l'Angou and... Ian Forrestal !!
Spiritual Intervention
[nec] Strike: dodge. [NEC] Strike: combat ends.
An excellent strike : combat end cards, no cost, wich allows you a quick exit when there are too many crows and wolves around.
Summon Soul
+1 stealth action. [nec] This vampire gains 2 blood. [NEC] Remove this card from the game and move up to 2 cards from your ash heap to your library. Shuffle your library afterward.
This necro-restoration offers at superior a very
interesting recursive power. If you don't play with Pochtli, this card can make the difference you need at the endgame where each card counts. Interesting if you have less than 90 cards and / or need lots of blood, otherwise, I'll always prefer a Whispers or Gear Up. Combo : Tower of London, Akhenaten if you dare play him.
Torment the Soul
[nec] Strike: 1R damage; not usable on the first round of combat. [NEC] Strike: 1R damage, aggravated; not usable on the first round of combat.
Until K:MW, the only aggressive Nec strike. It already wasn't good because the Giovanni had Potence. Now, even the Harbingers have good Nec strikes, and this card is definitively good for the worms.
Whispers from the Dead
[nec] Move a library card from your ash heap to your hand. Discard down to your maximum hand size afterward. [NEC] As above, but with +1 stealth.

Bring back the card you need right now.
Interesting even if you play with Carlotta. Get back counter cards (Deflections, Sudden, Delaying Tactics...) or what you need for your combos (Seduction / Call / Dom bleed). Wonderful when your hand is full of useless crap at a point of the game.