throwhemon wrote:anytime a unit is mentioned in a battalion from another faction it will become the allegiance of the battalion (this is mentioned right above the name of the battalion).
Taken from the designer's notes on the core rule book page 6.
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).