Fanwork rules?

I was wondering what the rules are revolving fanworks of this World of Warcraft IP?
There are tons of fanwork from multiple creators in many forms, many in the shape of drawn art or modelling.
Then there are also a few creating whole TTRPG systems or campaigns from the game itself cause sadly the original release of a Warcraft TTRPG went poof.

I was wondering what I’m allowed to create and do I have to get permission somehow?

No u dont.

Is that a no to creating content at all or do I not need permission?

Just credit it properly and you shouldnt have problems.
Fan service technically is a breach, but they wont bother with you until you start literally robbing them and even then- highly questionable someone with bother you as an artist.
If something is about to go down, they will first have to send you a warning too.
So you overthink this too much.