Thank you both, full power is now unleashed! Sorry for my stupidity, I missed a door on the second level (the one with the water in the back).
First off, I did not get the judgement bug, I have more like a "do this final thing" bug. The description on the item says (screenshot attached), that I have to "Travel to Oathbinder's Sanctum and rest at the altar." and boy have I rested there. With the weapon equipped, with in in the inventory, stash, hell I have put it even on the altar (the little bowl) and rested. Nothing. Anyone got a clue for this problem? Thank you!