I haven't had that many games with the Lore, but I must say I really enjoyed using it (in a non competitive environment). I tend to pair up my level 4 Dark Magic Sorceress with 2 units of 5 Warlocks and a two tower list, which gives me 2 heavy combat units that fight their fights pretty damn well on their own.
Power of DarknessI'll only swap to this spell on a level 4 in a large battle against a combat focused enemy. It's not something I like to rely on, but I will use it when my Sorceress ends up in combat, to get out of it. Most of all, I'll take when the other spells are lackluster.
Doombolt, la creme de la creme.
The fact this is a signature spell is perhaps the single most important argument in favour of this Lore for me. It's one of the top answers against what I fear the most: monsters, chariots, mobile troops that can't get caught so easily.
Chill WindUsed it only once. I'd consider it against Wood Elves and Empire but I didn't face them lately. Against Dwarves the low strength makes it ridiculously weak.
Word of Pain The unboosted version should have been three points cheaper to cast to be in line with other lores and usable for a level 2. It could have read "reduce BS or WS" since it's extremely unlikely you'll benefit from both anyway... yet we're paying for it.
Aside from that, I love it. It's miasma and enfeebling in one. It has uses before combat, and in combat it ensures a quick victory. The spell just works.
Shroud of DespairI've only had limited success with it so far, having never succeeded in a leadership bomb. But then I rarely needed to so far.
BladewindIt's not brilliant.. I usually have other priorities but I might keep it around against some opponents, including shooting units.
Soul StealerI seriously dislike the new mechanics. Too much rolling and checking for a mediocre spell. I bothered casting this only once so far but that's also because my Sorceress rarely was in danger (my troops chew through the enemy rather quickly).
Black HorrorI cast it only a couple of times and struggle with it, but I struggle with Vortexes in general (cast 3 purple suns once with only 3-4 kills against Dwarfs).
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So why would I pick this lore over another? Because with a level 4 it's likely to give me the two spells I like the most: Doombolt and Word of Pain. All the rest is mediocre, but nice to have.
Doombolt really helps me out so much it's unbelievable, and it makes the Lore infallible. Yes, I like it that much.
It might be the result of a very limited metagame that's dominated by Elves (High and Dark) and Dwarfs, with the occasional Chaos Warriors, Daemons, Wood elves and beastmen.
I rarely saw the need to take another lore than Dark Magic since the new book.
Vs Lore of MetalI like lore of metal. More importantly, it's a lore I want to love and like but unfortunately it failed me miserably quite a couple of times. Searing Doom is rarely cost effective, and this immediately weighs on the Lore as a whole.
I regularly end up with rubbish spells, which are severely limited by range (and the boosted versions narrow you down to one or two spells unless you get lucky) and applicability.
For this Lore to work, I need a lot of spells in it to open my options but Tome of Furion is no longer available. Now I would dare only to use it on a Level 4... Which I should try again one of these days, I suppose.
Vs Lore of LifeI simply haven't played this lore a lot. Last time I did, I felt I lacked options. It didn't translate so easily to results for me. It's something I have to work on.
Vs Lore of ShadowThis would be its biggest competitor, I think. The Lore of Shadow rarely disappoints me, thanks to Miasma but I haven't found any particular reason to pick this one over Dark Magic. I do like Pit of Shades but it's a bit limited in use. Mindrazor is amazing, but Word of Pain usually does the job. It's definitely a Lore I'd try again.
Vs Lore of DeathI should probably go to tournaments and watch how it is used, because I don't seem to get it
I struggle with the purple sun, and the rest "works but never makes wonders happen". I should try it on a dark steed mounted Sorceress some day. I just never bothered, since Dark always worked out on foot for me.
Vs Lore of BeastsNot tried it with my Dark Elves yet. It looks promising but feels wrong