Hoo Mjuu, The Torrent drops this item. It's level 16 or 17 (I forget which) and it's stats are as follows (to the best of my memory, which isn't very good, because I haven't been able to get one of these yet.):
Usable by: Almost all the classes. Certainly all the ones you'd want to use a staff with.
I know it adds to your MP and HP as well, though I don't recall how much it adds. It also has an effect on some of your other stats. It's -5 to something. It'd be really cool if someone could post the full stats of this thing, because it's a pretty amazing weapon, especially for a beastmaster. (Charm w/ staff.. wait.. wait.. let pet die.. macro equip axe. Go finish enemy)