Models and Fluff
In my last post, I praised the Vanguard, Ranger, and Ironstrider models. The model line only got better with the Sicarian Infiltrator and Ruststalker models. GW topped it all off with the Onager Dunecrawler.
I love the look of all these models, particularly the long-legged Sicarians. Their torsos and upper legs are clearly those of human beings, but their multi-jointed lower legs are grotesque cybernetic alterations that give them phenomenal mobility. This is reflected in their Dunestrider rule, which gives them an additional 3" of movement during the Movement phase, while running, and when charging. I prefer the look of the Sicarian Ruststalkers, but I think the Infiltrators' Stealth, Infiltrate, and Neurostatic Aura (which reduces a nearby enemy's WS, BS, I, and Ld by 1) will be a lot more useful.
I'm also a fan of the crab-like Onager Dunecrawler. The walker is obviously of human design and, like the Ironstrider, clearly shares characteristics with the Imperial Knight (the fleur-de-lis makes yet another appearance). At the same time, it has an insectile design that makes it completely different from anything we've seen fielded by the Imperium of Man. GW has even given the Onager a clever backstory.
As diehard 40K nerds already know, the High Gothic of the 41st Millennium is essentially corrupted Latin, although GW seems to throw in a healthy dose of Greek, too (paleontologists also love to mix up their Latin and Greek when naming dinosaurs). "Onager" is Greek for half-donkey or mule. This High Gothic name for the weaponized crawler was intended to be a translation of the name of its original utilitarian version: the "Mars Universal Land Engine" or "M.U.L.E." The M.U.L.E.'s design was inspired by the (apparently long-extinct) Terran beast of burden, which the designer mistakenly believed was insect-like.
The original M.U.L.E. was used to escort early Martian settlers across the planet's wastes. Since the Mechanicus is nothing if not a slave to tradition, Skitarii Battle Maniples of the 41st Millennium are still centered around their Onager Squadron.
Leadership and Doctrina Imperatives
Contrary to my expectations, Skitarii are not fearless. However, their base Leadership is as high as that of Space Marines while also having a number of ways to boost its value. We also know now that Doctrina Imperatives boost the BS or WS of the army for a turn. If the boost is merely +1, no other characteristics are affected. However, if the boost to BS or WS is +2 or +3, then an increase in BS will adversely affect WS or vice versa. There are currently six Imperatives, each of which can only be used once per game.
Initially, I had assumed that Doctrina Imperatives were based on a Leadership test since the White Dwarf revealed that "Data-tether" wargear added 1 to the Leadership of a unit affected by an Imperative. I wasn't sure how this was going to work for Skitarii vehicles since they also had the special rule. However, the codex states that to use a Doctrina Imperative, you simply choose one at the beginning of the Movement phase; all units in the army with the Doctrina Imperatives special rule benefit from the Imperative unit your next turn. Apparently, data-tether wargear is meant to reflect the fact that a unit affected by a Doctrina Imperative is subject to a higher level of external control by the Mechanicus Tech-priests, which has the side effect of increasing their effective Leadership for that turn.
Detachments and Formations
Since Skitarii lack an HQ, the standard Combined Arms Detachment is not an option. Instead, the basic Detachment is the Skitarii Maniple, which has no HQ choices, two mandatory Troop slots, six optional Troop slots, four optional Elite slots, two optional Fast Attack slots, four optional Heavy Support slots, and one optional Fortification slot. The Skitarii Maniple gives Preferred Enemy to your Warlord (who is chosen from among the Skitarii Alphas of your Vanguard or Ranger Squads, or from among the Princeps of your Infiltrator or Ruststalker Squads) as well as Scout and Crusader to all models. The universal Scout is limited in that units can't use it to Outflank unless they have the native ability to do so; e.g., Infiltrators, which have the Infiltrate special rule. The Skitarii Maniple seems like the best way to field a 1500 to 2000 point all Skitarii army.
The Battle Maniple Formation appears to be one of the best ways to field 800 to 1250 points of Skitarii with another force. The Formation consists of one unit of Vanguard, one unit of Rangers, one unit of Ruststalkers, one unit of Infiltrators, one unit of Ironstriders (either Sydonian Dragoons or Ballistarii, either of which can have up to six walkers), and one unit of Onager Dunecrawlers (which can have up to three vehicles). The Battle Maniple has all the special rules of the Skitarii Maniple while also giving Leadership 10 to all models within 12" of an Onager Dunecrawler.
For a reasonably balanced 2000 point force, you can run two Imperial Knights and a ~1250 point Battle Maniple. Unfortunately, you're limited to a single squadron of Onagers. The Onager is easily the most flexible unit in the codex. While the basic model has extremely limited close combat ability, if you upgrade it with a Cognis Manipulator, you get a Strength 10, AP1 close combat attack that also gives the vehicle It Will Not Die. (Bear in mind that its WS, I, and A aren't great, so don't get it in a fight with a Dreadnought or a Soulgrinder.) The walker's ranged capability is much more impressive, and has anti-infantry, anti-flyer, and anti-armor options. However, since all vehicles in a squadron have to fire at the same target, it's inefficient to arm each Onager with a different weapon.
For larger games you can field a War Cohort, which is composed of three Battle Maniples. All models in a War Cohort benefit from the rules of a Battle Maniple while gaining the ability to re-use a single Doctrina Imperative. I find the War Cohort appealing, in part because it includes three Onager squadrons, each of which can be equipped for a specific task. Unfortunately, my preliminary lists suggest that a reasonably effective War Cohort will cost at least 2500 points.