[quote=Skyrte]
I don't mind people making stuff up for their characters.
[/quote]

For the characters of course, that's how character creation works but this would be specifically about this cult you'd vaguely outlined earlier which means that it falls under your domain. If I was to integrate the cult into Avelina's backstory I'd entirely be making up my own stuff about them which may or may not contradict whatever it is you may or may not have planned out for them. 

If you don't mind I'll edit Avelina's backstory to include them.