A staff member mentioned that it makes somebody high just by looking at it. However, I noted a plothole in that if that were true then the gnoll wouldn't be in such a bad mode.
However....
What if the Magic Bong runs on magic?! It'd make sense that, however the gnoll acquired it, that eventually it'd run out of magic. Ordinarily a mage could just zap some spell points into it to recharge it but the gnoll doesn't know any magic. Thus he's stuck with an incredible device that he's incapable of using.