See an example here. My code for CSRF tokens is here.

I initially wrote these two bullet points but after comparing your code to mine these could be completely wrong. Take them as other potential errors in case changing your csrf token code does nothing:

1. You need an attachments item in your payload. It needs to be a string; '{"contentImages":[],"openGraphs":[],"atMentions":[]}' should work fine.

2. I'm fairly sure that you can't use JSON for message walls, so as well as json=payload you may also want to put params=payload

Alr, I'm going to try that..

Still not working with this code:

def getToken(WikiName):
    Token = session.get("https://"+WikiName+".fandom.com/api.php?action=query&meta=tokens&format=json&prop=revisions&rvlimit=2&formatversion=2").json()["query"]["tokens"]["csrftoken"]
    return Token
    
def postMessage(Text,Title,User,WikiName):
    payload = {'title':Title, 'wallOwnerId':User,'rawContent':Text, 'token': getToken(WikiName), 'attachements':'"contentImages":[],"openGraphs":[],"atMentions":[]}'}
    print(payload)
    print(session.post("https://"+WikiName+".fandom.com/wikia.php?controller=MessageWall&method=createThread&format=json",headers=headers,params=payload, json=payload).json())
    

Error 400 is specifically what I'm getting...

Dump the entire response, there should be a specific error message in addition to the error code 400.

Uh, there’s no error message. I try .json() and it just shows a blank list

Wait, I think I realised my error

If this works, I'll post my working code so more people can do this :D

• How are you creating the session? What endpoint are you using to login? Does the account you're using have 2FA enabled?

• Can you confirm that you're successfully retrieving a valid CSRF token?

• What headers are you passing as part of your POST request?

• As @TheWWRNerdGuy mentioned, the content type of your POST shouldn't be JSON; it should be application/x-www-form-urlencoded. Since it looks like you're using Requests, you should be passing your payload via the data kwarg (and not json or params). Try the following.

import json

def post_message(session, wiki_base_url, csrf_token, wall_owner_id, title, text_content):
    payload = {
        'token': csrf_token,
        'wallOwnerId': wall_owner_id,
        'title': title,
        'rawContent': text_content,
        'jsonModel': json.dumps({
            'type': 'doc',
            'content': [{
                'type': 'paragraph',
                'content': [{
                    'type': 'text',
                    'text': text_content,
                }]
            }],
        }),
        'attachments': json.dumps({
            'contentImages': [],
            'openGraphs': [],
            'atMentions': [],
        }),
    }
    return session.post(f'{wiki_base_url}/wikia.php?controller=MessageWall&method=createThread&format=json', data=payload)

Useing json.dumps and actually marking the jsonModel worked! Thanks :D