Core FAQ “Q: The rules say that a warscroll battalion can include allies and that they don’t count against the number of allies in the army. Does this rule only apply to battalions that share the same allegiance as the army, but that have units from two different factions (a battalion in a Daughters of Khaine army that has Daughters of Khaine and Stormcast Eternals units, for example)?
A: Yes. The faction a warscroll battalion belongs to is shown on its warscroll, above the title of the battalion. In addition, the battalion is assumed to belong to the Grand Alliance that its faction is a part of. Warscroll battalions that share the same allegiance as an army
can always be taken as part of the army, and if they include any allied units, these units do not count against the limits on the number of allies the army can have
(or against the points limit that can be spent on allies
in a Pitched Battle). An army can include a warscroll battalion of a different allegiance to the rest of the army, but if it does so the units in it do count against the limits on the number of allies the army can have (and the points for the battalion and the units in it count against the points limit that can be spent on allies in a Pitched Battle).”