How exactly do artifacts & faction bonusses work for allies? On the one hand I'd assume that none of em would be have any effect on the allies, but on the other hand there are situations like a tzeentch army taking Slave to darkness allies who then have the tzeentch keyword. Does Chaos just have a natural advantage as it's one of the few factions that can change keywords? Or is there some drawback I'm missing?
I cannot look right now but IIRC it is like this: Allies are all units in your list that don't have the common keyword of your allegiances and are not Endless Spells or terrain. Allies cannot profit from allegiance abilities, and they cannot take artefacts, spells from the spell lores, traits, or prayers, and they cannot be the General or Battleline. More (including my answer to your actual question) soon. Gotta split the post up because my phone glitches out right now.
Ok so what about those units that can gain the keyword through Mark of Chaos? I looked through the FAQ and GHB and it seems to me that those units are not allies. They gain the keyword when you write them on your army list, so they are part of the allegiance. So the way I read it a Chaos Sorcerer Lord in a Tzeentch army could take a Tzeentch artefact and spell, and Chaos Warriors could be battleline in a Tzeentch army. You can also take as many StD as you wish since they do not count toward the allies limit.
mm, neat if you play chaos I guess. Though for other factions a bit less so. Would be interesting if the other grande allegiance got similar subfactions that can be used to fill gaps in the same way.
There was an FAQ for core rules that also dealt with this. It stated that units that are part of any battalion gain the key word of the battalion. And that if a battalion did no have the keyword of your Allegiance that you had to pay for it with Allies points. This FAQ post is no longer in the Core rules FAQ or the Generals Handbook FAQ. I am trying to figure out if this is still the case as there were no announcements about its removal or an update on the Errata files time stamp.
I have spent a few hours trying to determine if this is still a rule. I can't find any official post about it anywhere. I know it use to be the Core Rules Errata. Perhaps GW changes their mind about battlions. Guess it is time to run Plague Touched Warband again. The entire Q&A section of the Core Rules Errata is now missing though.