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Celtic Name Pack (Invictus)

Tested. Adding files for the names in that way would add your lists to the vanilla ones, rather than replace them. You gotta use the 'nilla files (00_britannic.txt, etc)

And you would want, say, your "CNP_britannic.txt" in a subfolder titled "britannic".

Or at least, doesn't apply AFAIK. I'll test it real quick.

Your mod is a name replacer, so my advice on the GetS thread doesn't apply to your files (taking those steps would make the game load both the vanilla latinized names *and* your new Celtic ones). HOWEVER: Your CNP files, if you were only adding things, these lines would need to be removed (you want just the names):
color = hsv { 0.57 0.7 0.4 }
culture = {
#Britannic
britannic = {} #deprecated
caledonian = {}
iceni = {}
trinovantian = {}
cantian = {}
durotrigan = {}
dumnonian = {}
dobunnian = {}
demetian = {}
ordovitian = {}
coritani = {}
cornovian = {}
brigantic = {}
votadinian = {}
damnonian = {}
taexalian = {}
}

barbarian_names = { ANCALITES ATTACOTTI BIBROCI HORESTI CASSI GABRANTOVICES GANGANI NOVANTAE LOPOCARES SEGONTIACI SELGOVAE }

graphical_culture = celtic_gfx
ethnicities = {
10 = britannic
}

Good!
Thanks for the infos! I want to make my mods more compatible, I tried what you wrote in the Gladio et Sale compatibility thread (and other stuff) but I clearly don't know how to do it... I'm new to moding

Sorry about all this ^^' Thank you for being attentive.

I found the issue. Another mod touched cultures, so patched that one too. All good now.

It works when *only* your mod is loaded. So there's definitely something else in my load order that's not an obvious culture editor. I've narrowed it down to only a couple of mods that could be conflicting, and temporarily patched the base files of Gladio et Sale to play nice.

Tried everything you said but still the same...
But again everything is fine when I launch the game with my local files.
Do you still have the same problem when you launch only my mod?

Hmm... Try moving it to the bottom of your load order. If that doesn't work, try renaming one of the 00 files to something that doesn't match vanilla, like CEL_gallic.txt. This last option should, in theory, load your files alongside the vanilla ones without replacing them, so both namesets should spawn if the mod is working.