Here we are with the last, and smallest, section of the GSC Units to look over. Altho primarily an Infantry-based Army, there are some definite uses for some of the Vehicles they have available, particularly the Ridgerunner and the Goliath variants, which get a Cult Keyword and can benefit from some of the Cult-locked effects.
Achilles Ridgerunner: Speaking of the Ridgerunner, it's the first on the list, so let's dive in. There are a lot of potential ways you can set up a Ridgerunner to be used, but some of them are clearly better than others. It's a very light vehicle, with just a couple of extra Wounds separating its defensive Statline from that of a Sentinel, but it's substantially less disposable, coming at potentially over twice the cost of a Sentinel. This will definitely affect how good its various options are.
Other than the potential to explode (3", 1MW), the only unique special Rule it always has is Scout Vehicle. Before the first Turn begins, you can move it up to 9", staying at least 9" away from any Enemy Units. I'm going to have to play around with them for a while to figure out how worthwhile that actually is, because it also has Cult Ambush, allowing it to be held back while you just set up an Ambush Marker instead, but because of the timing of Scout Vehicle, it's mutually exclusive with Cult Ambush. I suspect it will vary case by case, but I feel like it will usually be better to keep it hidden so you can be sure to place it somewhere safe, and use Scout Sentinels if you want something that can move out from your Deployment Zone before the Game begins. Note also that this is a move, not a redeployment, so you'll need to go around any obstacles, potentially take Dangerous Terrain tests, all that sort of thing.
The Ridgerunner has three "main gun" options, plus a pair of Heavy Stubbers. Of the three, the Heavy Mortar is far and away my fave, partly because it's much cheaper than the other two, but mostly because it lets you keep the incredibly fragile Vehicle out of LoS. The Heavy Mining Laser is actually a pretty good buy compared to a regular Lascannon, but on a Ridgerunner, it's just too much of a glass cannon, and too tempting of a target for your Opponent. Similar to Brood Bros HWSs. I'd rather taken them on Rockgrinders. The Missile Launcher is just a Missile Launcher. It will function almost exactly the same as one taken on a Sentinel or in a Brood Bros Infantry Squad, but will be easier for your Opponent to destroy. Also, I must admit, I really don't like the design they went with for the Missile Launcher on this thing. It's too clearly a military weapon that was specifically designed for this Vehicle, rather than being a repurposed mining tool or something more improvised looking like the Mortar is. I'd rather see it done with something more like an Infantry Missile Launcher on a pintle mount, like some of the heavier armed pickups, or Technicals, used by parties that don't have the infrastructure for custom-built military vehicles.
The other three options are for different "support systems". If you do want to use a direct-fire Weapon on it, the Flare Launcher is a very attractive choice. Over the course of the Ridgerunner's 8 Wounds, the 6+++ roll will probably save you one of them, which isn't terrible, but isn't fantastic, either. It can also be used once per Game to basically give a Unit of Atalan Jackals the Turbo-Boost Rule for a Turn, which has some potential for shenanigans. A Spotter, on the other hand, gives you an extra 6" of range, which, especially with the Missile Launcher and Mortar, can help to keep it out of range of return fire. A bit. The third option, the Survey Augur, is the most expensive, but my fave with the Mortar, since it lets the Vehicle ignore the effects of Cover, and those are often going to be used on stuff that's trying to hide, which often involves both LoS blocking and Cover.
The Ridgerunner does get a Cult Keyword, but most of them aren't too great for it. Hivecult and Pauper Princes both have Stratagems which give it the potential to get +1 to Hit under the right circumstances, which is pretty nice. Ridgerunners can also benefit from being near a Hivecult or Bladed Cog Warlord with the Cult-specific Trait, and they can also benefit from a Jackal Alphus's Priority Target Sighted, the re-roll 1s to Wound against a nearby Primus's chosen target, and the Deny the Witch attempt from a nearby Magus.
Goliath Rockgrinder: I'm going to go out of Codex order here, and cover the GSC-specific Vehicles first, and then the Brood Bros options afterward. The Rockgrinder is as beefy as it gets for specifically GSC Units, with T7 and 10 Wounds, tho it is unfortunately stuck with just a 4+ Save. Rugged Construction gives you a 6+++ that should be good for another Wound or two on average, but isn't to be relied on. There are basically two ways I see to use a Goliath Rockgrinder. Either seems good, but trying to mix them and have it do everything is probably going to be bad.
First, and less fun, it's one of the few things GSC have that can really be a "bunker" type of Unit. It's not great at it, but between being cheaper and being able to get Cult benefits, it's actually probably better at it than a Russ would be here. The Heavy Mining Laser is your main option here, tho the Heavy Seismic Cannon might work. (IDK. I haven't really figured out what either version of the Seismic Cannon wants to be shooting at.) But the Heavy Mining Laser is at its best here. If you want, you can also toss maybe some sort of small counter-Assault Unit like a half-dozen Stealers or Acolytes in there, or even a Patriarch. Keep a Jackal Alphus or something nearby to help boost its accuracy, and you can probably get some real value out of it.
The more fun, and probably more effective, way to use it is as an Assault Vehicle. For this, you want to give it the Clearance Incinerator, and probably a Cache of Demolition Charges. Unlike in most Armies, the main use here isn't transporting an Assault Unit (tho you should probably stick one in anyhow, given how cheap it is to add on some Acolytes, and they let you use the Cache of Demolition Charges), but actually Assaulting people with the Rockgrinder itself. Depending on how damaged it is, it gets between 2d3 and 6+d3 WS4+ Attacks on the Charge, at S9, AP -2, Damage d3.
Keep Stratagems in mind when using the Rockgrinder. This is basically what Devoted Crew was made for, maintaining a Rockgrinder with even a single Wound as a major threat as long as you have CP left. Or if it does go down, and you bought the Cache of Demolition Charges, you can use Rigged to Blow to automatically make it Explode for d3 Mortal Wounds to every Unit within 6".
As with a number of other things in the GSC Dex, the threat of what a Rockgrinder can do is probably more useful than when it actually does it. The potential to just randomly shrug off that last Wound, the ability to act at full power for one more Turn, even what it can do when it does get taken out. You can't rely on any of those, but your Opponent has to keep those possibilities in mind when deciding how to deal with it. And any time you force them to make more decisions, you increase the chances of them making one wrong.
Goliath Truck: Now, if rushing an Assault Unit up in a transport is actually what you're going for, this is the variant you're looking for. It loses most of the Rockgrinder's offensive capability, and a point of toughness, but gains a couple of inches of movement until it's on its last legs, and can carry 10 Models. It does still have Rugged Construction, for that extra little bit of durability. It also has a Heavy Stubber and Twin Autocannon, which, if you'll pardon the digression, I really don't get, fluff-wise. A Heavy Stubber (or even two like on the Ridgerunner) seems perfectly reasonable. Even civilian life in M41 is pretty dangerous, and it's been clearly established that things like Stubbers are fairly common on Vehicles that are going to be traveling through sketchy areas. Almost all the other big guns (except for the Ridgerunner's Missile Launcher, which I have the same issue with) are re-purposed mining tools, which also make perfect sense. I could even see a jury-rigged Autocannon on there. But having twin Autocannon --heavier armament than that carried by AM Chimeras or even some Space Marine Razorbacks!-- as a standard fixture on a civilian vehicle just feels ridiculous. I really think it should start as a completely demilitarized base version, with all the weapons being optional additions. It would also make the thing about 28% cheaper if you just wanted to use it to haul dudes around.
OK, rant over. And speaking of hauling dudes around, that's the other upgrade it has over a Rockgrinder: A transport capacity of 10 (a Patriarch counts as 5). Now, that's not exactly optimal for most GSC Assault Units, that generally want to run Units of 15-20, but there's still some potential there. A couple of Goliath Trucks full of Stealers, Acolytes, or Metamorphs, and then maybe a Rockgrinder with a Patriarch and another support Character, or just a handful of support Characters, probably have decent odds of getting something across the board that's worth hitting folks with. Even more so, tho, they seem just about perfect for Aberrants. They have a max Unit Size of 10, and the Abominant doesn't take up any more room than any other, so you can really pack some serious hitting power into a single Truck there. Gotta be careful with it, because that's a lot of Points in one place, but if you end up across the table from someone who's clearly going to blow it away first thing, you do still have the option to just use it as a gun truck, and bring the Aberrants and Abominant in via underground tunnels. Do keep in mind that both variants of the Goliath are Cult-locked in who they can transport, which may be an issue when mixing Cults in a single list, but is more likely to cause issues with Brood Bros.
The other thing to keep in mind about the Goliath Truck is that it has the Open Topped Rule, which can make for some pretty nasty drive-bys with a bunch of Hand Flamers or something in there. And like the Rockgrinder, it has the option for a Cache of Demolition Charges, which both add some extra short-ranged firepower while you've got a Unit embarked, and unlock the Rigged to Blow Stratagem for it. As a final note, the Goliath Truck is probably the best statline to use as the basis for any Cult Limos anyone might have lying around or in progress/planning.
Cult Armoured Sentinels: I've gotta be honest, I really don't see the point of these, in either Astra Militarum or GSC Armies. They're slightly more durable than Scout Sentinels, but a Lascannon or Krak Missile can still one-shot them, and they lose out on the pre-Game Scout Vehicle move. They are one of the two places you can get a Plasma Cannon if you really want to, but they're pretty likely to just blow themselves up with it if you ever overcharge, since they can't benefit from any of the re-roll auras or anything that Cult Units can.
Cult Scout Sentinels: The main use I see here is the Scout Vehicle Move, as described above for the Ridgerunner, if you need a way to push forward before the game begins. That's less of a big deal than it was before the removal of Turn 1 Reserves, but there are some situations where you might want a bit of a buffer, or to get on an Objective right from the start, and with a starting price as low as 35 Points each, these guys are the most efficient way to do that. I probably wouldn't run them with anything but the Multi-Laser, since cheapness is their main virtue. It is unfortunate that they don't benefit from Cult Creeds and such, because the Sentinel Chainsaw upgrade would be mildly hilarious with Twisted Helix.
Cult Leman Russ: Nice and fluffy, but not terribly useful, I think. No Tank Commander option for Orders and better BS, no access to the best variants (Punisher and Executioner), and no Orders or anything to buff their accuracy. They are the only T8 Unit available, but given that we can't take enough of them to achieve Target Saturation, that doesn't actually mean much. Maybe when Allied with Nids using some of their T8 beasties? Probably still better to just take a Brood Bros Spearhead. If you are going to take one, the Battle Cannon is the best option. At first glance, the Eradicator Nova Cannon does have potential against T3 enemies, but for just a few points more, you can take an Augur Array with a Battle Cannon and get something significantly better. The Vanquisher is just plain awful, and the Exterminator is one of the only formerly Twin-Linked weapons that didn't get its shots doubled in 8th, leaving it badly under-gunned for how expensive it is. Heavy Bolters are the only Hull/Sponson weapons worth considering in most circumstances. Heavy Flamers are occasionally really nice, but most often useless, and pretty expensive for a contingency option. Lascannon, again, is just bad here. Plasma Cannon are slightly less terrible than on a Sentinel, because you only half kill yourself with an overheat, but still pretty bad.
Cult Chimera: Pretty much a side-grade from the Goliath Truck. Costs about the same or a bit more, depending on what options you take, has a little less firepower, but the extra point of Toughness and Save are probably worth more than the loss of Rugged Construction. The Lasgun Array more or less compensates for the lack of Open Topped, and pretty much everything else is the same. The first main thing about it is that, while the Chimera can't transport Cult-Keyword Models, it's the only thing that can transport Brood Bros, so if you want to haul them around, this is what you're using. It does still have Cult Ambush, tho, so you can make use of it in all those shenanigans as well. The other big thing is that it has access to a wider range of upgrades. The Dozer Blade is garbage, and the Auger Array isn't worth much here, but the Track Guards, letting you keep going at full speed regardless of how much damage the thing has taken, are potentially very worthwhile, if a bit spendy. An extra Stubber or Storm Bolter seems like a pretty obvious choice given how cheap they are, tho.
Bonus - Tectonic Fragdrill: It's a bonus because I completely forgot about it until just now ;) My gut feeling is that this thing really isn't worth taking in Matched Play. You can get a lot in a GSC list for 75 Points, and it eats up one of your Detachments as well. Maybe if we ever get a Fort slot added to one of the other Detachments or something. If you do take it, I kinda feel like the Drill itself is the least valuable part of it. What seems much more relevant is that it's a 10" tall piece of Terrain that provides Cover, and that you get to place during Deployment. And given how Cult Ambush works, you can actually wait until you've seen a pretty good chunk of your Opponent's Deployment before deciding where to put it. Then, on top of that, you can use it to send one Unit per Turn into the underground tunnels, popping back up wherever you want (usual 9" restriction from enemies applies) at the end of your next Movement Phase. That could be incredibly handy for late game Objective Grabs, effectively letting you bring in Reserves on Turn 4+, especially if you can keep them out of LoS while they're waiting.
I would note, however, that considered purely as a Terrain kit, it's a pretty good one. The drill blocks LoS to most of the middle floor, and if you choose to build it other than as the purchasable Fort, it comes with a couple of the most useful sprues in the Sector Mechanicus line (walkways and stanchions), is US$60 for a four-sprue kit (most of those are US$75), and has a ton of cool options for things to do with the drill, including some ways it can fit together with the Galvanic Servo-Haulers kit. Check out some of them on Ray Dranfield's twitter, and the_kit_basher on Instagram.
And that's all I've got. Sorry for not breaking it up with pics this time, but I've been writing this up because of insomnia, and now I'm finally starting to crash, and I can't deal with finding pics and putting them in. Hopefully I'll have some more finished Models over the next few days before the month runs out, but my hands have been pretty shaky lately, and most of what I need to finish up needs more care and precision than I've been able to manage. I may try to just slam out some stuff that doesn't need any fine detail work, or I may just go straight to the wrap-up/Army Lists portion of this review. Until next time, y'all have a good one now, y'hear!