if you use hacked items (items altered in a way not possible in DQ normally) in the Battle Arena, and someone checks the items and sees that they are hacked and then report them, then you could get banned by the Dev’s.
the Dev’s have said that they can’t do anything about players hacking items that are used only in Campaign mode, but PVP can be looked at to see items are hacked or legit.
basically, if you know which Crystals can be used on Eternal Items, or just compare against the items in the LegendEx, then you can know what items to report for hacking.
hope this helps.
there have been a few players who use hacks in their Campaign game but legit items in PVP, but all it takes is not paying attention one time and accidentally putting a hacked item in PVP. yes, there have been a few posts by these players.