I know some of you say beating Pandora's Box gives little, and it didn't give me much before but I beat it on level 30 and got 2 legendary and 1 rare item. I think it depends on whether or not legendary creatures appear which is random (I got a hydra and minotaur in my case).
 "Heavy Weapons"){kind=icon}
 "Monsters' Den: Book of Dread"){kind=icon}