Pulling out an oldie but goody from the Eye of Terror, with Gathering Storm II we have the “rebirth” of the Black Guardians, both as part of the Reborn Warhost detachment and a special formation called the Ulthwe Strike Force.
Black Guardians, Black Guardian Windriders, Black Guardian Vyper Squadrons, and Black Guardian War Walker Squadrons are based on their their “normal” Eldar counterparts, with a bump in points cost (+2 points per model for Guardians, +3 points per model for Windriders, +5 points per model for Vypers, and +5 points per model for War Walkers) and no access to Warlock squad leaders. For this extra points cost, the Black Guardians get a little more flexibility (they can either be equipped liked Guardian Defenders or Storm Guardians) and, more importantly, all four units gain the “Webway Assault” special rule, which gives them the ability to Deep Strike with no scatter, as long as they are more than 9″ away from any enemy units.
This ability to Deep Strike with no scatter, IMHO, is well worth the extra points costs and really bumps up the tactical flexibility and capability of all four of these units. What really makes them a competitive choice, however, is the Ulthwe Strike Force formation, which has the follow special rules: number one, if there are any Forces of Chaos units in your opponent’s army at all, the all members of the formation gain Stubborn and Preferred Enemy, which are quite useful but largely situational based on who you are fighting against. Second, and the real reason for taking this formation, is that if you include the max of four units, then you can begin rolling for them to come out of Reserves on Turn 1.
So, taking this all together, this means you can have four units of Black Guardians, Black Guardian Windriders, Black Guardian Vyper Squadrons, and Black Guardian War Walker Squadrons (in any combination) that can all come in from Reserve Turn 1, Deep Strike with no scatter, and then unleash massive firepower exactly when and where you want it… I think this is going to be a game changer formation and that it will work very well alongside other Eldar, Dark Eldar, Harlequin (Battle Brothers), Tau, and Imperium forces (Allies of Convenience ).
Here is are some thoughts on using each of the different Ulthwe Strike Force units:
 Black Guardians — I think the key with these ones are “go big or go home.” Given their relative fragility (i.e. T3, 5+ save) and the short range of Shuriken Catapults, you really want to Alpha Strike whatever your target is with maximum combat power and leave nothing left to attack you back with. Understanding that, if you take a squad of 20 Black Guardians with eighteen Shuriken Catapults and two Shuriken Cannon Weapons Platforms, you have the ability to put out 42 x BS4 S4 AP5 Bladestorm shots a turn at 12″ or less. That gives you the following average damage output:
*GEQs — 19 Unsaved Wounds
*Orks Boyz — 14 Unsaved Wounds
*MEQs — 8 Unsaved Wounds
*TEQs/Centurions — 5 Unsaved Wounds
*Riptides/Wraithknights — 3 Unsaved Wounds
*Daemon Princes — 6 Unsaved Wounds
*Hive Tyrants — 5 Unsaved Wounds
As you can see, from just one squad, that is some VERY significant damage output, so imagine pairing up two of these squads and Deep Striking them in with zero chance of scattering to vaporize a key enemy unit (or two) on turn 1. Of course, the key with this is to combine it with plenty of other dangerous threats so that you opponent doesn’t simply shoot your Black Guardians off the table the next turn in retaliation… I think things like massed Astartes Drop Pod units, massed MSU Eldar Jetbikes and Warp Spiders, Tau Battlesuit MSU lists, massed Astra Militarum Mechanized Veterans, Dark Eldar Raider spam, and/or Harlequin Troupe spam, can achieve this by providing so many targets that your opponent is over saturated (especially if you took out 1-2 of his key units turn 1 with a Black Guardian “alpha strike”).
 Black Guardian Windriders — We already know how great Windriders with Scatter Lasers are already, perhaps being the most under-costed unit in the game for the combination of mobility, durability, and firepower they possess. While Black Guardian Jetbikers cannot get Objective Secured and cost more than their conventional brethren, the ability to Deep Strike with no scatter Turn 1 makes them exceptionally potent units. Not only can you basically “null deploy” them (which takes away your opponent’s best chance of shooting them turn 1 and either destroying them or forcing them to Jink before they can shoot), but with no scatter deep strike, you can put their Scatter Lasers in EXACTLY the right place to engage enemy units with minimum threat of retaliation, hit the rear armor of enemy vehicles (usually AV10, which Scatter Lasers Glance on a 4+ and Penetrate on a 5+), and/or grab Objectives with no risk in a Maelstrom or Objectives heavy type mission. They get all this and still have all of the ridiculous mobility that Eldar Jetbikes are infamous for, making them a threat the entire rest of the game.
 Black Guardian Vypers — While not quite as dangerous (or cost efficient) as Black Guardian Wind Riders, a squadron 6 Vypers with dual Shuriken Cannons still puts out 36 x S6 AP5 Bladestorm shots at 24″ a turn, whether they are moving normally or arriving from Deep Strike, thanks to being a Fast Skimmer. Like with the Windriders, being able to Deep Strike with total precision means you can tear up the rear armor of an opposing vehicle squadron with maximum efficiency (i.e. on average, against AV10 rear armor, this squadron can drop 12 HPs a turn, which means they can kill an entire squadron of Leman Russes in a single volley). Additionally, due to the versatility of S6 and Bladestorm, a Black Guardian Vyper squadron can bring down enemy MCs or Heavy infantry with ease and even deal well with enemy hordes (i.e. a single 6 vehicle squadron with kill 20 Orks/Guardsmen/Cultists/Gaunts in one Shooting Phase, on average). Again, the problem is vulnerability to enemy return fire after they arrive, so placement and mutual support from friendly units is key to maximize the efficiency of Black Guardian Vypers. Finally, as a Fast Skimmer, Vyper squadrons can rapidly redeploy up to 30″ a turn, which makes them very useful for grabbing/contesting Objectives, getting into new firing positions, and/or escaping enemy forces that are closing in on them.
 Black Guardian War Walkers — Just like the three mentioned above, Black Guardian War Walkers are “glass cannons” with low survivability and very high damage output. War Walkers are the most expensive of the four options for the Ulthwe Strike Force, but in some ways they are the most versatile, with built-in Scout (so Outflank too), a 5++ save, the ability to tie enemy units up in melee in a pinch (since they are Walkers), and the ability to take two Eldar Heavy Weapons per model… this means you can kit them out for various roles, with everything from Heavy Infantry killers (i.e. dual Star Cannons, meaning a maxed out Squadron puts out 12 x BS4 S6 AP2 shots at 36″ a turn), Vehicle Hunters (i.e. up to 6 x BS4 Bright Lance shots a turn), or General Purpose Fire Support (i.e.dual Eldar Missile Launchers with 6 x Starshot, Plasma, or Starhawk missiles a turn for anti-tank/MC, anti-horde, or anti-flyer duties, respectively). Combine all this with Turn 1 no scatter Deep Strike and, in the hands of a skilled commander, they can be a finely-tuned “scalpel” for eliminating linchpin units of your opponent’s army before they even get a chance to engage.
Summarizing all this, you have to be careful and skillful when employing such fragile units, or your opponent will make you pay the price, but the ability to Deep Strike at the beginning of the game with no scatter is an exceptionally valuable ability for the entire Ulthwe Strike Force, making it a high-value ally for your army. One small note on maximizing this formation is that, if you can fit it in, I think it would be tremendously valuable to include an Autarch (via an Eldar CAD or Allied Detachment) in your army list, since his “Path of the Command” rule provides tremendous control over your Reserves and lets you reliably either bring in ALL of your Ulthwe Strike Force turn 1 for a massive Alpha Strike or, if necessary, keep them back until later in the game until certain conditions have been met (i.e. if you are playing Tau, eliminating some of their key units with Interceptor so they do not murder the Black Guardian forces as they arrive via Deep Strike).
Overall, I think this is going to be an exciting formation to play with and I am looking forward to trying it out as an ally in a couple of my current army lists.