Editing Warhammer 40,000/9th Edition Tactics/Adeptus Mechanicus (section)

===HQ===
*'''[[Skitarii#Skitarii Marshal|Skitarii Marshal]]:''' So remember how the Secutarii had their own HQ that supported his boys in various ways? Well GW finally decided to get off their asses and provide something like that to the modern-day Mechanicus as well. Totes a radium gun (thankfully assault, not pistol) as well as a weapon equal to a power maul. Very useful in that they allow a nearby {{W40kKeyword|<Forge World> Skitarii}} or a {{W40kKeyword|<Forge World> Skitarii Data-Tether}} unit anywhere on the board to ignore the penalty applied when using a Doctrina. The great weakness is that they have zero repair ability, so you'll need another HQ to cover that niche.
**Also provides a 6" aura of re-rolling 1s to wound for {{W40kKeyword|<Forge World> Skitarii Core}} units, which means for Skitarii, the Marshal is ''radically'' better than a Dominus, although they stack.
**Broadly speaking, has access to the best warlord traits, but sacrifices access to your Forge World specific warlord trait.  Accordingly, if your only WT models are marshals anyway, you have less incentive than usual to stick to a stock Forge World over a custom one.
**Has a particular lack of synergy with Vanguard, in that re-rolling 1s to wound is of no benefit if you auto-wound.  Assuming BS3+ Vanguard (so 1 in 4 of your shots that hit auto-wound), the benefit of a nearby Marshal is reduced from a 7/6 (1.167) multiplier to 9/8 (1.125).  With BS2+ Vanguard (e.g. from the Protector Imperative), the Marshal goes from a 7/6 (1.167) multiplier to 17/15 (1.133).
* '''[[Tech-Priest Dominus]]:''' Your ''cog''-standard non-Cawl HQ for those times you want to play as those other forgeworlds, no longer an "HQ tax" due to Enginseer changes. Akin to a '''Space Marine Captain''' (''aura of re-roll 1s to hit''), '''Techmarine''' (''repairs D3 wounds to any {{W40Kkeyword|AdMech}} model other than itself'') and a bit of '''Apothecary''' (''repair isn't restricted to vehicles, and can be healed by a fellow techie'') all rolled into one. At T4 5W 2+/5++ this very tanky support character will require serious firepower to remove. Just watch out for enemy witches. Its main concern is to boost and heal your firebase, whatever it might be (Vanguard, Onagers, Kastelans, etc.), but 24" guns allow it to be good at midrange since it doesn't give up shooting (BS2+) for repairs. A flexible loadout, it'll be defined by what you want it to do:
**'''Shooty''': Pick the Volkite Blaster and the '''Phosphoenix''' relic for good and reliable volume of fire, its range fitting nicely alongside Vanguard.  The Phosphoenix will help your Vanguard shoot through Dense Cover.
**'''Choppy:''' Go with the Macrostubber and the Volkite Blaster, and give it '''Anzion's Pseudogenetor''' for an additional 3D3 S+2 AP-1 hits on top of your 3 Omnissian Axe attacks and Pistol 5 Macrostubber attacks, the latter of which happen at BS2+.
**'''Repairman''': Give it the '''Necromechanic''' WT so that it restores a flat 3 wounds every time it repairs something. Fun to combine with the '''Tech-adept''' Stratagem to repair the same vehicle twice, repairing ''up to 6 wounds per turn'' that way, bringing an Onager back to full stats or keeping multiple Kastelans from dying.
*'''[[Enginseer|Tech-Priest Enginseer]]:''' The Enginseer is a perfect cost-saving option for an army trying to make a battalion and can be taken in the same slot as a Dominus or Manipulus ''or as an extra HQ option not taking up a slot with the new Brotherhood rule''. With T4 W4 3+/5++ it's basically a squishier Techmarine with lackluster combat ability, but that's ok because its main role is being a cheap repairman and HQ.
**'''Repairman:''' Repairs whatever a Dominus can at the end of Movement, and on top of that, during Command grants a friendly {{W40Kkeyword|vehicle}} model (aside from Kastelans) +1 to hit, which is something not even the Dominus can do. While no longer the same as the IG version, still useful as a budget buffer.  The big downside to the buff is that it happens during Command and wants to target models faster than the Enginseer is, which may give you difficulty in getting your support model to keep up with what they're babysitting.
***If all you care about is the +1 to hit, BS3+ -> 2+ is a 25% increase in output, which means for a 55 point model, it's worth the effort on a 220 point target.  That's more than any target you can field, which means you should never field an Enginseer just for the accuracy buff - make sure it's doing double duty as something else as well.
**Note that the Enginseer has very little synergy with the various Holy Orders - the +1 to hit they can grant won't work on any unit the Holy Orders can buff.  There are units they can ''repair'' that can be buffed with Holy Orders, but that's the extent of it.
**'''Relic Caddy''': They aren't champions like SM Captains are, but since most of their job is to stand around being available, they could just as well be useful by carrying army-boosting relics ''after'' you gave the Dominus/Manipulus theirs.
**'''Buying advice:''' Enginseers are a must-have if you want to fill HQ slots, at only 55pts per model for a small, tough character that can heal vehicles. The only problem is that they cost $30 a pop, unless you go for the $11.50 metal ones from the webstore. An alternate solution to that starts with looking closely at the chaos cultists in the "dark vengeance" kit. The robed ones look remarkably like Enginseers, right? Hell, one has an axe that looks remarkably like a cog. You can buy them for 20 bucks on eBay and kitbash them with the ton of bits leftover by your Skitarii squads, techpriest Dominii and Onagers. A little work and you have your all the Enginseers you need for less than the cost of one. Another option would be the Forge World titan tech priest! A lot cheaper than the Enginseer, and Forge World quality too! Another Option that you DEFINITELY want to consider when trying to reinforce your army is actually buying the Start Collecting: Adeptus Mechanicus Box. Great if you planned on getting Skitarii Vanguard/Rangers and the Dunerider anyways since it effectively saves you about 60 (57) bucks when paying 95 dollars for the box, essentially you're getting the Rangers and half of the Enginseer for free.

*'''[[Tech-Priest Manipulus]]''': In the command phase, boosts 1 unit's arc/radium/galvanic rifles with +6" range and gives them an additional -1AP. Ridiculous on a squad of 20 vanguard, very impressive on 20 rangers!
**The problem with this guy is his cost relative to what he does: even under absolutely optimal conditions where he's buffing a 20-dude Vanguard unit with nothing but Radium Carbines in it, he raises the cost of the whole shebang from 160 points to 230, which means it's only worth it against Sv2+ - against e.g. MEQ, you're gaining 33.33% damage output for a 43.75% increase in cost.  The benefit he provides to Galvanic and Arc rifles is ''less''.  At best he should be your third pick behind a Marshal and a Dominus.
*'''[[Technoarchaeologist]]:''' The generic version of Daedalosus from the Blackstone Fortress game, acting as a support HQ to a Dominus or Manipulus. His weaponry is unique for an HQ but nothing special; he carries a Servo-Arc Claw and the pistol version of the Eradication Beamer.  Instead, his real benefit comes from his special rules. He emits a 12" aura that shuts off enemy deep strikes. On top of this, he can pick a friendly {{W40kKeyword|<Forge World> Core}} or {{W40kKeyword|Servitors}} unit within 6" during the command phase, letting Kataphrons perform objective actions and allowing the chosen unit to perform objective actions as well as shoot.