Greetings DarthWolf!
Thank you for reaching out to us and welcome to our forums!
Situations like yours may indeed occur due to the usage of Mods in your game.
We understand that you’ve tried without mods, but please perform these actions in the following order.
1 - Please uninstall and remove your Mods completely. Then, reinstall your game.
2 - Additionally, please verify your files by going to your Conan Exiles on Steam → right click it and go to ‘‘Properties’’ → Installed Files → and click to ‘‘Verify integrity of game files’’.
3 - Please check if the Arcane Staff is working in one of our Official Servers.
4 - Make sure you have the neccessary requirements to cast a spell.
If in none of these cases the Arcane Staff is working properly, please send us a video of you attempting to use it.
We’ll be waiting for your reply!