It’s time to discuss the new Adeptus Mechanicus codex. It breaks the line of the different space marines books, which we could see since the beginning of the 8th edition.
The main thing is that Skitarii and Mechanicus are now in the same book. Moreover, they are united with the same forge-world keyword. That means that all aura and abilities now work on them equally. Quite logical – this was expectable since the release of their first books. Especially, considering the fact that most players used combined formations anyway. Besides, Imperial Knights are also included in this codex. They have a different keyword, but they can be repaired by Mechanicus, and there are special stratagems for them.
As for the characters, there are two new ones – expected Belisarius Cawl, and Enginseer, who used to live only in Astra Militarum codex. And he’s a nice choice since he provides a cheap repair\healing for your units. However, you’ll likely choose Dominus or Cawl a warlord. And Cawl is pretty good in it. Mostly because of the total re-roll to hit and the chance to add\substract 1 to the canticles result. (They are the same like in the Index). However, this makes you choose the Mars Doctrine. It’s not bad at all (2 doctrines per turn are great, especially with Cawl’s ability) – but it devaluates the other doctrines. Yes, there are some nice choices, but nothing competes with this one. And it doesn’t improve the variability.
Now the Mechanicus doesn’t have even allied transports. Considering the low mobility of the most units, you’ll likely choose a gunline strategy. And Cawl is a perfect choice for it. This tactic is also supported by the other units. For example, transuranic arquebus, which used to be a weird choice, is now one of the deadliest weapons in the game, able to target characters all over the board. Fill in the troops' slot with rangers (they are cheaper now) with arquebuses and enemy warlord won’t have a single chance to survive. Plasmas and vanguards are still a nice choice, but they require convergence, which is hard when you have slow and easy-to-kill units.
Battle servitors will still remain popular (at least, destroyers), nonetheless most of their weapons have lost in effectiveness. Plasma seems the best one – nice range and potentially a lot of shots. Such servitors can form the first rank of your gunline – they are able to hold the enemy for a while since the unit is quite tough.
And the quintessence of our gunline – Castellan robots. Their fists are cool, but now each one can fire 9 shots with heavy phosphor blaster. And under the special protocol – twice this many. And they have a decent strength and AP. Also, the unit itself is hard to kill – each robot is a small tank. And do you remember Cawl’s re-roll to hit?
Also you can add a Dunecrawler with neutron blaster – now this weapon looks more effective than the others. And if there are spare points – a Knight with range weapons. He doesn’t get re-rolls, but you can fix him and even use the stratagems that give him benefits from the canticles.
What’s unexpectable – electropriests are really improved. Both kinds. Considering stratagems which strengthen their close combat and shooting, they can be a very fearsome enemy now. However – slow and vulnerable. So, it might be reasonable to keep them in cover before the enemy comes closer to your gunline.
Walkers are the only ones who don't seem to have a place in this army concept. Their cannons are heavy – so prepare to 4+ to hit (if only they don’t work as a static lascannon in the gunline). Dragunes are nice – quite fast, dangerous in close combat. You can capture the objectives and control the battlefield with them.
Artefacts are also not diverse – mostly there are powerful versions of usual weapons. There’s only couple – healing one and the one, making your overwatch better. There’s also noting to say about stratagems – they improve particular types of units, and you’ll use all of them, depending on what unit you need right now.
So, is codex Mechanicus a bad codex? No. It can be deadly and effective. The problem is that it lacks variability that we had in all the 8th edition books. There are still few units and gunline is still the most effective strategy. We have no transport and deepstrike – so, there’s nothing left. However, it may be only the first impression. Playtests will show.