Playing as Chaos and.... (Potential Spoilers)

[Faeronsword]

Wissenland allies me and becomes part of Chaos undivided? I was really surprised when this happened.

I'm not so familiar with Storm of Chaos era lore, so I'll take what I can get.

Has anyone else had this happen? Or is this just some random event?

[RCOG]

Having played a Khorne campaign, the league of Ostermark 'fell to heresy', which resulted in them allying with me and taking up the flag of Khorne, later as Chaos undivided a similiar event happened with the county of Nordland.
Im fairly sure there's a reason or way for the mod to determine which of the factions 'become corrupted by chaos', but I have no idea how, or in what way it relates to the lore.

~Regards RCOG.

[Kahvipannu]

It's random, it can happen even for the player as playing Empire. There is some variations that affect it, and killing the faction-leader stops the worshipping of Chaos.

[BigHairyMelon]

Might have something to do with the number of churches you build or how many the AI build?

[IrishBlood]

Its caused by the religious percentage and how high/low the faction leaders piety is. The best way to prevent it is to have warrior priests take out as many heritics as possible. If your playing as an empire faction and you want to make sure your allies dont fall to heresy then put ALOT of warrior priests in any provence that has its empire religion drop below 60%.

[Swad]

Ah, so if I want to attack the other empire factions legitimately, I should put my faction leader in a province with a chaos temple and let him sit there until he turns and my faction joins with chaos, right?