As far as I remember the Staff gives :
raw: exceptional quality, 10% chance natures' mark on hit, once by encounter
first upgrade : can cast two beetle's shell per rest (200 hp cocoon on target, the target can't act) per rest.
second : 10% chance twin stones on hit, once by encounter
third :superb quality, can cast ironskin 3 or two times per rest.
Maybe the powers are differents for druids or monks, I haven't tried it yet.
English is not my first langage, so abilities granted by the staff may have another name.