Shiny key BUG

[halow1213]

I'm lvl 28 blade DANCER name of the pj: ancienttouch.

I was upgrading my weapon in the dark glimpse to get the chest that would give me my corrupted item so i could do the break throught. I decided to use that shiny key to open the chest so theortically it would drop a item for my class, but instead of that it dropped a blade master sword... Idk if this is normal or a bug so it would be great if anyone can help me.

Thank you.