[DEV Question] Why is this allowed?

[Louvain]

It is very possible that they were doing the level 50 relic quest and forgot they had it on. Anyone else also could have noticed beforehand and pointed it out to them as well. Unfortunate that it was caught after the run was done, but you cleared and they don't appear to have weakness, so they knew how to do the fight to some extent. The weapon could have been unintentional. If it was though then... :/