The readme file says under Import > Step 4. to import Vampirism.iml, but that file is also in the .gitignore so it is not in your repo.

Did you execute the previous tasks?
gradle setupDecompWorkspace ideaModule should generate one for you.

It is in .gitignore, because it contains user/device specific configurations and thereby, does not help anyone else.

Did that work for you?

Closing because outdated and no response