I already leveled this to max on my Cipher but severed binding and put it on my fighter.  I went back to oathbinder altar again for final stage for fighter but it does not successfully upgrade when resting at altar.

Is it only able to be maxxed on 1 character or is this a bug?

Hey Sapient,

 

Based on what you've said it sounds like a bug.  I put a report in to have this investigated so the QA and Systems Design teams can confirm that the cudgel is acting improper and see if they can get a fix in.

 

Thank you for reporting this to us!