A Suit of Stealths
Apprentice
I understand this may have been suggested before, but we have potions for stamina, health... why not mana? Not only would it prolong several fights in player versus player, it would also be an interesting replacement for the quite useless Night Sight potion. Perhaps you can use that one's ingredients to make a mana potion or something like that, who knows. Nevertheless, might be an added bonus to being an alchemist.