In a Nutshell: The Lore of Dark Magic

Lore Atteibute(s):
Spiteful Conjurations (Dark Elves):
This one is kind of bad. It can be nice, but it's not all that useful. Every time you cast a spell on your enemy (I believe everything but an Augment spell) it inflicts 2D6 S1 Armor Piercing hit on the unit distributed as per shooting, provided you roll a double on the power dice when casting. 3D6 if you roll triple. It can be nice, but it's not really something you should be banking on ever. It's like getting a free Flock of Doom every time you cast hurtful magic at someone. I've seen it take off a whole Ogre before, but that's literally best case scenario. Can be nice, more often then not blows cock. It's no Shield of Saphery to be sure.

Warth of the Wood (Wood Elves):
Whenever a Wood Elf successfully casts a spell from this lore, and the spell is not dispelled, place a Vengeance Counter (I just love that phrase! Sounds like a spell from Final Fantasy!) next to each target once the spell has been resolved. Whenever a unit with a Vengeance Counter suffers a hit(s) from a spell in the Lore of Dark Magic remove the counters and increased the number of hit inflicted by D3 for each Vengeance Counter removed (roll separately for each counter). Remember how I said Lore of High Magic works best with a combat Wood Elf army? Well, Dark Magic works best with that hardcore guerrilla fighting style army. The ability to use these things to just nuke an enemy unit to dust in the Magic Phase is very helpful in that kind of build, because your shooting is good, but the meta is really working against you full force if you're relying on the shooting phase to carry you to victory. Remember, only a Level 3 or 4 can take this lore for the Woodies, so this attribute is going to be more useful then you might initially think.

Signature Spell #1: Power of Darkness
God! All these things sound like they belong in a Final Fantasy game! This spell is every bit as useful as it's snobby cousin in the High Magic department. For a casting value of 8+, the caster targets the unit she/he is in and they get +1 Strength until the start of the caster's next magic phase. This is really, really nice, but it gets way better! Additionally, you may add D3 power dice to your power pool. If three dice are generated, the caster suffers a wound with no armor saves allowed. Two things make this spell incredibly awesome. First, it's perhaps the best spell in the game to open up a magic phase. From here one of three things will happen. First, you throw two dice on it and get it it off (assume we're using a Level 4). Your opponent must either waste dice to stop it, burn his dispel scroll, or suffer because you've just prolonged the magic phase and made your unit much scarier. Second, you get it off and roll a 5 or 6 to generate more power dice. Your casters should have Ward Saves, and in a Wood Elf army the Lore of Life is very accessible. Meaning you can heal your casters who do suffer a wound. Dark Elves have access to Life magic as well, although I poo-poo any Dark Elf player who takes an order-based magical lore like Heavens, Life, or Light. Third, you roll a single die and miss it. It's a single die, not all that big of a deal really. This spell is very powerful, and with some of the less impressive ones, I would highly suggest swapping for this bad boy right here. I give it an easy 4 out of 5, and a recommendation to swap for it when necessary.

Signature Spell #2: Doombolt
This is the utility MM spell out of the lore and a damned fine Signature Spell at that. It's got a base casting value of 12+ and a range of 18". It inflicts 2D6 S5 hits, but it can be boosted to inflict 4D6 S5 hits for an increased casting value of 24+. This spell is basically the utility killer out of the Lore of Dark magic. It can be used to take out chaff and thin enemy ranks alike. S5 is pretty damn powerful, but this spell's obvious drawback is it's casting value. I've never seen it boosted before, but I'm sure if you need to clear out rank-and-file infantry than this is the spell for you. I give it a 3 out of 5 due to it's high casting value, but it is still a very powerful spell. If you're playing an army that isn't going to be all that affected by the #6 spell in this lore, then I suggest you take this one instead.

Spell #1: Chillwind
This spell is a Magic Missile with a range of 24" and a base casting value of 5+ that inflicts 2D6 S2 hits. If the target suffers any unsaved wounds, all the models in the unit suffer a -1 penalty to their Ballistic Skill until the start of the caster's next magic phase. The only good thing about this spell is the ridiculously low casting value paired with it's 24" range. If you remember I managed to rage pretty hard about the uselessness of The Flock of Doom. This is half of a step up from Flock, but this is still pretty fucking awful. Switch for Doombolt if you roll this POS. 1 out of 5. It's a godawful spell people, it really is that bad.

Spell #2: Word of Pain
A Hex spell with a range of 24" and a base casting value of 9+. All models in the targeted unit suffer -D3 to their Weapon Skill and Ballistic Skill until the start of the caster's next magic phase. Roll once for both stats. It can be boosted to have a casting value of 12+ but now the spell also effect the targets' Strength and Initiative. This spell is what allows elves to just fillet through entire hordes of infantry without getting so much as a scratch on them. I highly recommend this spell, especially if you're running a combat style army (this is the only time I go back on what I said, I promise). I give it a 4 out of 5, I've had entire hordes decimated because a Supreme Sorceress jammed this down my throat in combat with a horde of Executioners.

Spell #3: Bladewind
This is a Direct Damage spell with a range of 24" and a base casting value of 9+. Every model in the targeted unit must pass a Weapon Skill test or suffer a Strength 4 hit with the Armor Piercing special rule. This is a really nasty spell when combined with Word of Pain. Throw this on turn 1 when your combat blocks are still far away from each other. The guy lets it go because he's waiting for the nastier spells, then boom! Bladewind comes in and decimates the unit. Really freaking great against Orcs and Goblins, makes Night Goblin buses disappear like Houdini. It's also good because it targets a rather obscure stat, something that I think a lot of people really underestimate. If your Woodies, use this on the Death Star units you can't take out with bows. I give it a 4 out of 5.

Spell #4: Shroud of Despair:
A Hex spell with a range of 12" and a casting value of 10+. Until the start of the caster's next magic phase, the targeted unit cannot benefit from either the Hold your Ground or Inspiring Presence rules. In addition, whenever a target fails a Leadership test, that unit suffers a -1 to their Ledaership until the start of the caster's next magic phase. This spell is very kinda, sorta useful. The first part is absolutely amazing, and finally puts an end to those fucking Skaven Slaves rolling around at Leadership 10 with a re-roll. As for the Leadership shenanigans, eh I could honestly leave that for a cheaper casting value and some more range. Not a bad spell to have if you have a lot of monsters or Fear/Terror causers, but as a whole I am not too impressed. I give it a 2 out of 5, but not a recommendation to skip it completely because again negating high Leadership from the General and re-rolls from the BSB can be a very pivotal tactical edge.

Spell #5: Soul Stealer
A Direct Damage spell with a range of 18" and a casting value of 11+. It's a Magic Vortex that uses the small round template, scatters D6", and inflicts a S2 on any model under it with no armor saves allowed. Now, up until now, this spell is kind of crappy, but here's where it gets interesting! Roll a D6 for each unsaved wound inflicted by this spell. For every roll of a 4+, the caster gains a single Wound (to a maximum of 10). You can boost this spell to have a range of 36" for an increased casting value of 14+. If you're a Dark Elf player, swap for Doombolt. If you're a Wood Elf player, use this to annihilate those hordes of T3 infantry you can't take out just with arrows and make your caster MUCH more survivable. I give it a 2 out of 5 with a recommendation to look at what you're playing against before swapping for it, especially if you're an Eco Terrorist.

Spell #6: Arnzipal's Black Horror (AKA; the spell no one of the human race can pronounce) 
A Magical Vortex with a casting value of 15+ that Remains in Play and uses the small round template. However, unlike other Vortexes, I dig the shit out of this spell! You get to pick what direction it moves in by rolling the Artillery Dice and multiply your caster's level by it and that's how far it goes. Any model under the template must suffer a Strength test or be slain outright, although the model may take a single Ward Save if it has it. If a misfire is rolled, center the template over top of the caster and then scatter it D6". Regardless of a misfire or not, in the subsequent turns (which I presume to be every magic phase), it scatters and moves the distance equal to a rolled artillery die. If a misfire is rolled, it collapses in on itself and is removed from play. It can be boosted to use the large round template for an insane casting value of 25+. This is proof that the Dark Elves are absolute insane sons of bitches. I can just picture Malekith and Morathi sitting in their tower and being like (most likely Morathi I think); "Wait a minute! What if we take the precision and reliability of Dwellers Below and combine it with the sheer power and insane range of the Purple Sun of Xerseus?" This spell is fucking metal. It is the only Vortex spell in the game  I actually like, and think about that people, think about how much I rant, rave, and hate on Magical Vortexes! I give it a 5 out of 5, it's a fucking beautiful spell that would be very difficult to decide it needed to be swapped for.

So that's Dark Magic, and what do I think? Well, much like High Magic it depends which army you're playing that has access to it.

Dark Elves; This lore is really great in the same way High Magic is great for High Elves. Getting the +1 to cast is really a powerhouse in terms of just getting shit done in the magic phase. Plus, there's a lot of spells that can neuter much tougher opponents, allowing the faster and more skilled Dark Elves to cut them into ribbons at a whim. The one caution I would give Dark Elf player about this lore is that it is NOT a direct replacement for the Lore of Shadow. I've seen a lot of people run it as such, and then forget that there's no Miasama or Okkam's in this lore. It also has a lot of synergy with the lores of Shadow and Death, which are always mainstays of a Dark Elf army. Other then that, I highly recommend rolling with this on your Level 4 while using your support casters to snipe characters and bubble out really nice Augment and Hex spells with Death and Shadow respectively.

Wood Elves: If you're running an army very heavily reliant upon shooting and avoidance style fighting, then I highly suggest that you take this lore to assist with scything down those annoyingly protected characters and elite units. Things that most Ballistic Skill based shooting can't take out with some major nice rolling. Now, this will be a bit of a trade off since you're trading the ability to protect yourself with most Augments that other lores have access to for a much higher rate of firepower. Again, remember that only your Level 4 has access to the Lore of Dark Magic. So keep him in a forest and keep him very well protected. That's the only thing I can suggest, other then that it's up to you.