Potions: Only 2 in the game, but you can steal one after giving it to one patient = 3rd cure <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" /> - the pickpocketed one remains cured.
Magic mirror: which one? Aleroth (duplicates the healing gems for the ill soldiers) or from the Blue Boar Inn (useless)? Though the magic mirror from the Inn is part of the stuff you can buy from the trader. After having spent 2500 gp, you get one skill lvl in trader's tongue.
Both elixiers: give back mana/vitality - not much, it's better to sell them
Alchemy spoiler link, click here[/b]Nope, you can't join the [b]Black members/assassins
Bottle: Yes, you can steal it from Anthrabert - or buy it(quest solved)
or you wait until the wagon's burning and then go back to his room = bottle is on the floor (quest unsolved)
Kiya - from trying-to-be-evil to good <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />