As the title shows

This is caused by this line: https://github.com/Alex-the-666/Rats/blob/f3d41648a00c6d51a75ca0d6b0a79a35906b0900/src/main/java/com/github/alexthe666/rats/server/CommonProxy.java#L169
Do not use the vanilla registries.

@diesieben07 where's the Line for this same error AlexModGuy/Ice_and_Fire#3070

You didn't even post a debug.log there. Also, you should let the repository owner figure that out, I am sure they know best where their dodgy registration code is.

fixed