Ok, this is a big one. In 3e, Bonereapers were mechanically defined by their immunity to battleshock and extra command points plus extra commands to use them with. Before that they were also defined by their champions and elite units being able to issue commands - though that was made game-wide. But with bonus command points no longer allowed and battleshock no longer a thing, the question of what even would be their thing has been hanging for a while. The other big question for me is Mortek Guard unit size. We've seen a push to tie unit size more closely to box size (hence nighthaunt dreadblade harrows now being a unit of 2 instead of individual heroes). Will mortek guard be going to units of 20 to match their boxes?
Well it turns out OBR's new thing, at least in terms of faction rules, is basically a version of ossiarch commands, only no longer tied to command points, instead they're now limited by being 1/phase (with two to choose from in each movement, charge, and combat phase, including your opponents), and usable only by heroes, effecting all units wholly within in a 12" bubble of that hero.
I have very mixed feelings about this. On the one hand, they look like good abilities. A 12" bubble of +1 rend vs. charging enemy units until end of turn, usable in every enemy charge phase? 12" bubbles of 5++ or +1 to wound usable in every combat phase? 12" bubble of +2 move or withdraw-and-charge usable in every movement phase? that's all great stuff.
On the other hand, narratively a major part of why and how Nagash designed the ossiarchs was to specifically have an undead army that /wasn't/ dependent on their heroes to keep them functioning, so basing the army's faction abilities entirely on their heroes feels out of character. Remember how ossiarch champions and elite units being able to use commands used to be a faction defining thing, specifically because the army wasn't supposed to rely on heroes? Additionally, everything being a wholly within bubble will force the already slow army to bunch up, further limiting their ability to occupy the table and contest objectives, and considering that taking and holding territory is also a big part of ossiarch fluff, again, this feels off.
The previewed subfaction is +1 to cast for OBR infantry wizards, and before you ask soulmasons are classed as 'infantry' for some reason, so that's fine. Vokmortian also benefits. I've wanted this for OBR for a long time, so I'm stoked.
As for warscrolls...
We don't get to see Katakros or Arkhan.
We do get to see Vokmortian. He's still a double caster. Instead of his wonky and difficult to pull off worse version of hand of dust, he now has a new version of mortal contract as a signature spell, which fits him better narratively. it only lasts till start of next turn, only punishes the target for targeting a specific obr unit instead of any obr unit, and the d3 damage roll fails on a 1 - so it's a lot worse than current, but still maybe decent, and a double caster (potentially with +1 to cast) is still plenty good what with how lore access works in 4e (empower nadirite weapons works more or less as you'd expect and is unlimited, so that's solid). He's also got a new 1/game signature ability that tags an enemy unit in any (most likely your enemy's) hero phase, and for the rest of the turn non-fight core abilities (move, charge, shoot) cost a cp for that unit to use, which should be pretty effective. All in all, he looks pretty good, so points dependent Vokmortion may ~finally~ be coming off the bench.
Especially as Soulmason is reigned in a bit. Still a double caster (again with potentially +1 to cast from subfaction), so still looks good, but his signature spell is strike first instead of +1 to hit, and he doesn't get to cast it d3 extra times per turn, so he's not just 'better vokmortian' anymore.
Stalkers lose their dread falchions weapon upgrade, and hunt & kill, and a wound, and their aspects are weaker - no +1 damage, no +1 save. Hammer units seem to be somewhat reigned in across the board though, so they could still be quite solid relative to the rest of the field. The base profile of their blades is still 4 attacks, 3+/3+/-2/1, which looks pretty decent in 4e, especially that rend 2 with an aspect for another +1 rend vs. heroes.
Crawler looks to have seen a solid upgrade. still 24" range 4 attacks, 4+/2+ instead of 3+/3+ is ~slightly~ worse, but more than compensated by damage increasing from 2 to D3+2, the addition of anti-infantry (rend+1) making it rend 2 against infantry, and the general reduction in save stacking across the board. It lost its special ammo, but still has a chance to make enemies strike last, though it has to concentrate fire on a single unit to do so. All in all this looks to be a HEFTY boost to the crawler, in an edition where shooting in general is getting toned down. I'm hyped for it.
the abilities on spearhead warscrolls don't reflect the full game abilities, but the statlines supposedly do, and the kavalos spearhead profile and weapon stats seem... ok. control 1 feels low for them, though. Looks like we'll be depending on mortecs for capturig objectives.
All in all, I'm pretty happy with what I'm seeing here, and am particularly hype for actually-playable vokmortian (assuming they don't do something stupid with his points cost) and +1 to cast subfaction. The faction abilities seem good, even if they aren't the direction I would have gone with for the previously discussed reasons.