Lovely Assistant: Magical Girl by bitterkarella

A magician's assistant has two very important duties, to point at things and to look good in a form-fitting evening gown. But when Mugwort the Magician is kidnapped by his devious riddle-obsessed arch-nemesis and imprisoned somewhere on his opulent magician's estate with no way to find him other than a series of obtuse riddles, it's up to consummate magician's assistant Trixie to save the day!