When taking Imperial Guard allies, there are some things to keep in mind. First, you can only take Imperial Guard Infantry Platoons until you take two, at which point you may take 1 Rough Rider squad, 1 Sentinel Squad, and 1 Leman Russ Battle Tank (Note: if it were up to me, I would say that taking multiple Leman Russ tanks isn't possible, but ask your opponents or a tournament adviser if you can take an entire squadron). In my opinion, the only things worth taking are the Platoons and the Leman Russ, but taking two Platoons is a hefty point investment so I won't cover Leman Russ tanks. You can read a bit more on that here. While this may seem like a redundant post as I covered a lot of what you can get out of allies in that article, I'm going to expand on it here. Some obvious reasons why to take Imperial Guard are for the much needed anti-tank and some transports of your own. Plus, you can hold objectives easily with any remaining guardsmen. But I'm getting ahead of myself a bit, so first I'm going to list these orderly below.
- Anti-tank options through meltaguns on the Platoon members or special weapon squads.
- Access to Heavy Weapons such as Autocannons or Lascannons for Anti-tank/heavy infantry.
- Allows (cheaper) Chimeras to be used on other infantry squads such as Grey Knights or even Terminators
- Adds a lot of bodies to absorb fire or hold objectives.
Inquisitorial Stormtroopers are actually one of the cheapest meltagun per pointcost in the game, and they have Ballistic Skill 4, something Imperial Guardsmen taken from the Platoon don't have. Only Imperial Guard Veterans can compete there, but they can't be taken in a Daemonhunter force.
As for Heavy Weapons such as Autocannons or Lascannons, Grey Knights can't really do much there, other than the lascannons probably coming from your Heavy Support options. If you feel you could use more long-range anti-tank, Infantry Platoons are probably your best option. But, you will spend at a minimum 170 points for two lascannons and while you can acquire more by investing in Heavy Weapon squads, the points can add up quickly. Plus, not being in a squad with throw-away troops will cause them to die quickly, especially against Strength 6 or higher weapons and if they aren't in cover. However, if you are going for Heavy Weapons, Heavy Weapon squads are very cheap when it comes to heavy weapon per point cost (60 base, +5, 10, or 15 per gun depending on if you invest in heavier weapons or not). If you do take them, I really recommend only going for the Autocannons or Lascannons. Other weaponry is just not worth the amount of points going into these guys. For a point comparison, for 485 points, you get 11 Lascannons and lots and lots of guardsmen. A lot of points, but of course you can take 2 or 3, you don't need to take 11.
The Chimeras are a bit of an impossible argument. They are a really big benefit, especially seeing how you cannot even think about taking them without allies, but they are expensive. Not so much in point cost alone, but in the fact that you have to take a large amount of Guardsmen to get them. Okay, it isn't all that bad. For 130 points minimum, you can take 55 point Chimeras that comes with a multi-laser/heavy flamer/heavy bolter and a heavy bolter/heavy flamer with 15 point extra armor if you want it. I can't really recommend how to kit these out all that much as I haven't done so myself, but it depends on how you want to use them. You only have 5 shots out of the Chimera and a couple more from the vehicle itself, but you do get a lot more mobility and a lot of more survivability. It is something I would like to try myself, but I haven't had too much time for experimenting. Plus, I have other reasons I'll hold onto until later. Most likely, I would try out a Multi-laser and a Heavy Bolter, the default option. Unless I put Incinerators in there, at which points flames would be coming from every corner, which goes without saying. Plus, you can throw down a couple Heavy Weapons and hold objectives, too, trying to get use out of every point you put in, which is the most viable thing to do.
So, a lot of arguments and counter-arguments and arguments within those. I hope it wasn't too much rambling and you readers out there could get something from the post. So, the point still stands. To Ally, or Not to Ally? Why not give it a spin. Try proxying some models or borrowing some from a friend, put some Guardsmen and Chimeras on the field and see how the game goes. You have to be aware of some strategy changes though. You will have to give up on one unit, which will probably be a troop choice or something. Without that, you won't have as much assault/counter assault power. So, playstyles change. Going all out offensive isn't going to fit as well, even with the Chimeras. Chimeras can zip around, distracting units or pecking at weak squads or even giving cover saves to Land Raiders or squads, but you don't want to throw yourself at the enemy and assault if your opponent is ready for it. I'll try to post back with some better tactics when throwing in Imperial Guard, as I'm not even sure right now. If you don't have a copy of Imperial Guard, you might want to find one to borrow from a friend or maybe just ask someone on the internet for help with point cost and statlines. If you need anything, post a comment and I'll do my best to get back to you on it.
There are some other reasons for sticking away from allies. Perhaps you play a 3 Land Raider list, where this strategy doesn't really fit. Or, at lower point games, it is tough to squeeze in the guardsmen without hurting your Grey Knights too bad, and it might be better just to stick with Stormtroopers. Or, maybe, like me, you don't think it fits a "fluffy" list. Grey Knights would rarely actually work with Imperial Guard, let alone sit in Chimeras! Thinking about it more and more made me realize that Grey Knights with Imperial Guard isn't much different than throwing in Inquisitors or Stormtroopers. But even if you cast it off as heresy, you should try it out once or twice. Heck, maybe even trying out Imperial Guard with Grey Knight allies (I think I might try that out some day...). Just experiment, it is part of having fun with the game.
Before sending this off into the blagosphere, I'll give a quick "unit swap" on how to fit a couple Guardsmen and Chimeras in your list. For me, I just dropped my Incinerator squad and added in a Platoon with a Lascannon in each Guardsmen squad and 3 Chimeras, also dropping Master-crafted on my HQs weapon and some smoke launchers on Dreadnoughts. Though I think I'm going to have to redo some things, as I think I could drop one Chimera for now... I'll make a post soon enough focusing on some of my army lists and I'll include a revised version of this one. Hope you enjoyed this post and were able to pull something through it. Let me know how you use allies if you do. Do you go full out, practically playing Imperial Guard under a different name or do you subtly put a squad in? Post here how everything works out for you and hopefully that will improve my army list post for the rest of the crowd.
EDIT: What I guess I should really hammer home is that playing Imperial Guard allies doesn't have to take away from a Grey Knights list fluff-wise and even somewhat playstyle-wise. You can actually add new units to your force to reinforce some weak points and play a fun and perhaps a bit more competitive army. Let your new units add to the fun of your list, not take away. If you don't have fun playing a list with Imperial Guard, then don't play a list with them. Honestly, it isn't a big change in gameplay. Give it a shot and maybe you will be surprised at the results; allies add to the fun, not taking away from it which seems to be the general consensus but they are also not necessary which some seem to believe.