Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

If my army has a Slaves to Darkness allegiance, but uses a Godsworn Champions of Ruin battalion and has an allied Daemon Prince in there, is that rules legal? (since Daemon Princes are not StD, but a permitted unit in that battalion).

All I saw about that is if my army has the models to make a battalion, I pay the battalion points and then I can use it, but didn't find anything else about battalions regarding allies.

If a battalion has an allegiance listed at the top of the page, everything in that battalion counts as being part of that allegiance. They don't gain the keyword, though. They just don't count against the allegiance of the army. In this case, a Daemon Prince in a Godsworn Champions of Ruin counts as a Slaves to Darkness unit.