[mayegelt]

Ahh this old chestnut again...

The general consensus is that the allies rules are written badly and uses the word "Faction" to frequently to both describe the armies and collective group of armies (such as Forces of the Imperium).
Technically as written if you wanted to you could have a CAD with Space Marine Chapter Master as HQ, Leman Russ tanks as Heavy and Grey Knights as Troops in the same CAD if you read the rules as written. This is because as "Forces of the Imperium" they are all the same Faction.

The other weird one is because of the Space Marines FAQ it says something like
"Space Marines can be taken as an allied detachment even if your army's primary detachment contains units of the space marine faction, provided they use different set of chapter tactics"

HOWEVER though I don't have the FSE book, I know that from Crimson Slaughter (CS) & Black Legion (BL) they both say in clear words they treat CSM as Battle Brothers and count themselves as CSM for the purpose of being allied to. Also they may ally with CSM. So in this case you could have CSM Primary with BL Allied Detachment OR Combined Arms Detachment.

HOWEVER (again) the Iyanden book does not say either way about allying to Eldar. Though in the case of Iyanden there is no point in doing so,
Iyanden can still take the special wargear from the Eldar book, so long as they don't also take any of the special wargear from the Iyanden book on the same character.
They can freely choose the Eldar or Iyanden Warlord Traits.
They suffer no penalties such as having to take particular things or being denied anything apart from Spirit Seer must take Voice of Twilight instead of Conceal/Reveal as Primus for their powers.
Basically Iyanden just get bonus rules of being able to have Wraithknights and Wraithlords as Warlords. There Spirit Seer also get a different Primus Power. Also they can take Spirit Seers in 1-5s as a single HQ choice. As said above they also get some extra wargear and warlord traits and extra city of death and planet strike types of things as well.

 

[mayegelt]

What stops this one from happening is the Codex's own Force Org Chart. Yes, BRB says that you can have the same FACTION as your primary CAD, but the Codex writes out the Force Org Chart that says you can't have a Leman Russ without the rest of your Force Org, your hQ and Troop requirements. Nothing in the BRB stops that requirement (except unBound).

Well only some books have their own FoC, though the ones in the rule book are different to those ones anyway, and it says these are the ones to use in the BRB unless you want to use one of the unique ones with their own rules a codex has.
The big weird one that normally throws the spanner at the suggestion by me is as I said with this whole "Factions" thing what appears to much and actually refers to different things in different parts of the rule book. Is that for instance if you have a Imperial Fist Space Marine army, as written if you read 1 way you could not ally with anyone of the same faction (as it says allied detachments must have a different faction to the ones in your primary detachment) would mean that you could not have Grey Knights or Imperial Guard or Space Wolves or whatever because they are the same faction (Armies of the Imperium). But would of course be able to include anything from any of those books in the same Primary Detachment as all of them would be the same faction. The Faction being, Armies of the Imperium, and the only restriction being on a CAD / PD being that all units contains in it must be of the same faction (being Armies of the Imperium).

I think the people who checked the rules to make sure they were well written died when Nuffle did.

 

[mayegelt]

Since I don't have my BRB7E in front of me, I can't respond as well as I'd like to. End result: Can you find something in the BRB that says whether a CAD can use multiple armies? The default rules for a CAD apply in most cases, and I believe there are restrictions that say all entries in a CAD must come from the same codex. However, since I can't quote it verbatim, I'll leave that one in the air.

Talking about using multiple codices in a singled CAD leads back to what I mentioned at the top of this post, in which I feel that there's a restriction in the CAD saying all entries must be from the same source.

All the CAD thing says for restrictions is that everything in it must be the same Faction or no Faction.

So the arguement becomes as i said what "Faction" they mean. At one point it says that Faction refers to the army (aka Space Marines, Blood Angels, Grey Knights, Daemons...) though only a couple of pages on it says that your Faction is things like Armies of the Imperium and such so things like Grey Knight, Blood Angels, Space Marines, Space Wolves, Astra Militarum, Inquisition... are that Faction. Though of course only the Imperial ones tend to get this as the big problem / boost to their armys. CSM of course kinda get it with CS and BL. Eldar as a said doesnt matter. I dont know about the new spacewolves expantion or ork one as well.

So if you are using the first example of Faction above as your reference then you can have only the stuff from that book or shares that books army Faction (so allowing stuff like FW gubbins what is Blood Angel in a Blood Angels army for instance), this also allows you to have an allied detachment of things like Spacewolves or whatever with your Primary Blood Angel Detachment.
The other side of the coin is if you use the word Faction from the 2nd example. This would allow as i said before things like a Grey Knight High Lord (HQ) Dark Angel Deathwing Terminators (Elite), Imperial Fist Tactical Squads (Troops) and Astra Militarum Leman Russ Tanks (Heavy) and of course all the normal FW Gubbins. This would be due to them not breaking the restriction on being 1 Faction as they are all Armies of the Imperium. BUT they would not be able to use an allied detachment to get any of those armies counted as Armies of the Imperium as this would be allying to the same Faction.

Generally I would think it is universally accepted that for the CADs and stuff it means Faction and not Faction. Unlike me though, they didnt colour code the book

 

[mayegelt]

Simply put, any supplement is now the same faction as the core race. You can always CAD them, but you can never Ally them. With the exception being Marines, because they treat each Chapter as its own faction in terms of using an Allied Detachment.

This isn't right either though. As the Black Legion and Crimson Slaughter say you can ally to CSM and class as CSM for the purpose of being allied to.
Otherwise Marines gain an advantage of "We have different Chapter Tactics so we can." While BL and CS have effectively the same deal as chapter tactics (unique special rules & relics, restrictions in unit choices and/or mandatory choices imposed on them).

As I said before with Iyanden. The first line of their rules basically say "These guys count as Codex : Eldar, but have these additional rules." As I have also said their is actually no point in Iyanden ally with Eldar because the supplement is filled with bonuses with no drawback (outside of spirit seer cant take conceal/reveal).

 

[mayegelt]

Yes Ntaw, that probably works

 

[mayegelt]

So yeah as the full part of that post says.

Black Legion counts as Black Legion for Faction
Crimson Slaughter count as Crimson Slaughter for Faction.
For instance BL could have an AD of CS or CSM.

Clan Ruukaan however class as Iron Hands, so could not AD to Iron Hands, but could AD to Ultramarines for instance.