Editing Warhammer 40,000/8th Edition Tactics/Adeptus Mechanicus (section)

===Heavy Support===
*[[Onager Dunecrawler|'''Onager Dunecrawler''']]: Your best bet at dealing with heavy armor, and with plenty of solid options. a 3+ 5++, and their '''Emanatus Force Field''' allows them to reroll 1s on invuln saves if another Dunecrawler is within 6 inches.  They can no longer squadron, so taking a few will eat your Heavy Support slots.
**While the Skorpius Disintegrator may have greater shooting utility, volume, and consistency, the Onager has the durability, due to the disintegrator lacking an invulnerable save.
**'''Turret:'''
***'''Neutron Laser''': Never leave home without one. Heavy d3 48" S10 AP-4 Dd6 and treats 1's and 2's on damage rolls as 3's. The most expensive weapon option, but two or three Neutron Lasers will cripple or destroy even the strongest vehicles. Do note that the option to take a Neutron Laser is '''Neutron Laser and Cognis Heavy Stubber''', which gives you both weapons (paid for individually points-wise), with the stubber mounted under the laser itself. Note that the way the rules are worded, a Neutron Laser Dunecrawler with a Cognis Heavy Stubber can purchase a second Cognis Heavy Stubber as well, giving you 6 s4 shots to pop off besides your big gun. A worthwhile investment. In a pinch you can use 1 CP for Protector Doctina Imperatives and have this nuke a flyer out of the sky on a 2+ (only if you have the broadspectrum data-tether, but why would you not)?
***'''Icarus Array''': It slices, it dices, it makes everyone cry. If you field more than one Dunecrawler, always field one of them equipped with an Icarus Array and a '''Broad-Spectrum Data Tether'''. 10 shots at BS2 against anything that has the FLY keyword (hint hint: skimmers, jumppack/jetpack infantry, fliers, etc) means it will handily rip and tear anything apart, or take a good chunk out of it. Particularly brutal against Tau and Eldar of all flavors, since most of their vehicles are skimmers. It hits other targets on 4's, however, With the '''Protector Doctrina Imperative''' Stratagem, the Icarus Array transforms into a terrifying anti-infantry gun with 5 S7 shots and 5 S6 shots hitting anything on 2's. 
****Alternate Opinion: Unless you have a full brigade you might wanna save your command points. Especially since your vanguards and infiltrators are far better against the conscript/boyz/gaunt-blobs that are so strong in 8th. Your onagers are better used taking out actual fliers or tanks. (It does hit on 4s naturally anyway. No need to get greedy with your Icarus BRRRRRRT Array.)
****Alternate Alternate Opinion: If you're ever aiming it at conscripts/boyz/gaunts you are doing it wrong. When not aiming at flyers it's best at shredding medium to heavy infantry, light vehicles and "monster" units. Basically anything that falls between T4 to T6 with multiple wounds on it.
****Very good with Mars. Cawl's full re-roll makes the -1 to hit against non-FLY units a minor inconvenience, and it gets great utility out of moving from S7/S6 shooting to S8/S7 with the canticle.
***'''Twin Heavy Phosphor Blaster''': 6 shots at S6 AP-2 ignoring cover is good for deleting MEQ units, not a bad choice by any means, but it's outshined by the '''Icarus Array'''. Not the wrong choice if your meta is filled with MEQ, but vs hordes the Kastellans can pack 3 of these per unit against one Dunecrawler, before doubling their shots.
****The Icarus array packs a Gatling rocket launcher that is basically the same gun minus one shot with four extra autocannon shots but hits on 4s instead. 
****The Dunecrawler kit also isn't super magnetizing friendly to the Icarus array, so between building this or a I.A; you're probably better off magnetizing the I.A. and placing the little cover on the side instead of the missiles and proxying it. 
***'''Eradication Beamer''': D6 shots is quite random, but on average it will fare decently well against both vehicles and infantry. S8 means it will wound t4 targets on a 2+, and t7 vehicles on a 3+ (Same as the Neutron Laser). The difference is in the AP, which is only -2, and it only does D3 damage per shot unless you're in 12 inch range (Which you never want to be in, anyway). A good deal cheaper than the '''Neutron Laser''', but it will always feel like you're shooting an inferior version of it.  
****Best used against {{W40Kkeyword|Necrons}} as their special shielding rule tends to be ineffective on D2/3 damage rolls, and  wearing down your opponent is better than having the damage ignored altogether.
**'''Emitter:'''
***Sadly, you want to take two of these for the Emanatus, but the tethers don't stack (only making the bubble bigger), the doctrina stratagem targets a specific unit, and these models can't squadron..
**'''Smoke Launchers''' gives enemies shooting at your Crawler -1 to hit for one turn, but you have to give up shooting. It's extremely situational and not recommended. Stacks with the Stygies dogma.
**'''Cognis Heavy Stubber''' is a straight-up addition, coming in at 2 points for a 3-shot bolter that can be fired on the Advance at a -2 (though why you would want to Advance the measly 1d3" your Crawler gets is beyond me). This is the one that the Skitarii is firing from out of the hatch, and is separate from the Neutron Laser weapon option (which includes another cognis stubber). Just buy it, at 36" range it will rarely be out of targets, and removing a single wound of literally anything in game earns back its points several times. You're mounting it on a t7 3+/5++ chassis that has easy access to repairs, as well as numerous other defensive buffs, it will last a while to get its shots off.
*[[Legio Cybernetica #Kastelan Robots|'''Kastelan Robots''']]: More slot-efficient than the Dunecrawler, as you can get 6 in a unit. (Spamming them is a trap though, since they're extremely vulnerable in the Fight phase; 2-4 is enough.) They still have the same Monstrous Creature statline, and can reflect guns back at their shooter (for a Mortal Wound now), but are now faster and cheaper.  Fully shooty is actually the cheap option now. Go full phosphor and enter protector mode for 18 S6 AP2 shots per robot. Yes, a full unit of 6 will fire 108 bullets... In protector mode becomes twice as good as any unit we have. Beware combat with this option though, as without the Fists, you don't have any AP in close combat.  AdMech now has fewer ways of dealing with high Toughness, and Kastelan Fists in Melee will punch holes in virtually anything, so consider fists if you are lacking in Dunecrawlers.  It's recommended if you are going shoot, deck them out with 3 Heavy Phosphor Blasters, or if you are going punchy, get Fists and the Incendine Combustor.  Don't mix the Combustor and Phosphor options together, they don't synergize well.
**Protector Protocol is great for shooting, but don't underestimate the other modes.  Aegis Protocol will make your Robots even more tanky, with 2+ Armor and a 4+ Invul, and Conqueror Protocol lets them attack twice in combat and just fisticuff anything to death.  In general, Fist Kastelans will prefer either Aegis or Conquerors, while Shooty ones will want to stay in Protector Protocol as much as possible.
**It would be great if the reflection worked like in 7th edition (where *any* saving throw of 6 reflected), but now it is only Invulnerables of 6, and the Cover Bonus from Shroudpsalm only increases the armor save.  Unfortunately, the Aegis Protocol Trolling of the Index is now gone, so you will only reflect a Mortal Wound on a Invul Save roll of 6, after re-rolls but before modifiers.
**A critical difference here between {{W40kKeyword|LUCIUS}} and {{W40kKeyword|Stygies VII}} when deep striking is that the former deep strikes in after it's too late to change Protocols outside of Binharic Override (costing a second CP for the unit), so unless you're willing to shell out the CP, you'll be in Aegis Protocol on the turn you arrive.
**Speaking of Binharic Override, if you are running shooty robots, it may be a good idea to just use ASAP to get your Kastelans doubling their rate of fire on the first turn, rather than having to wait until turn 2.
***Be certain if you do this that they are where you need them to be for the rest of the battle, as they will no longer be able to move.
**The amount of overwatch shots and natural 6 STR is probably enough to keep most CC units away, even more if you're screening.
**They do make incredibly good [[DISTRACTION CARNIFEX|Distraction Canifex]].
**If you still feel like you need avoid CC at all costs, switching the shoulder phosphor weaponry to Incendine Combustors can be a valid option : as Protector Protocols works during any phase, 6 robots doing 12d6 S5 AP-1 hits to a charging unit, + the 72 shots of Phosphor Blasters should stop most charges in the game. However, don't let that Rhino or Knight charge you, m'kay ?
*'''[[Skorpius Hover Tank|Skorpius Disintegrator]]''': If it’s mobile firepower you’re after, you’ll want the Skorpius Disintegrator. It comes baseline with 3 Cognis heavy stubbers and a prow-mounted disruptor missile launcher that packs a highly explosive wallop: 36” Heavy d6 S7 AP-2 Dd3. Random attack numbers and damage make it unpredictable but it is a ''decent'' weapon nonetheless. It also comes with a broad spectrum data-tether and canticles, as well as ignoring heavy weapon rules unless it advances. It has the exact same stats as the Skorpius Dunerider, except for an additional point of toughness (T7). Probably the most critical difference when deciding between this and the Dunecrawler, is the invuln save, or rather lack thereof on the Disintegrator. So in summary, the Disintegrator has better firepower for the cost than the Dunecrawler but is less durable, which means it can be shot off the board dishearteningly fast. 
**'''Turret:'''
***'''Ferrumite Cannon''' 48” Heavy 3 S8 AP -3 D3. An excellent option for reliably blasting chunks from enemy vehicles, monsters or elite, multi-Wound infantry, thanks to no randomness in shots or damage. As stated in the Dunecrawler section, this weapon does statistically less damage than the neutron laser against enemies of >T9, but fails to account for the missiles, which can even out this damage loss. If your opponent fields a lot of really tough things pull out the dunecrawlers, but otherwise the disintegrator and its cannon will do fine to kill whatever it is you want, as the points cost is nearly the same (116 vs 117--crawler with two stubbers and laser).
***'''Belleros Energy Cannon''' 36” Heavy 3D3 S6 AP -1 D2 and can hit things out of LOS. A decent amount of shots make it a good contender for medium infantry killing and the LOS capability means you can park behind obstructions and hide from tank killers while still remaining mildly effective.