Marchesa is a graduate of Krull's own college of wizards and in command of the flying disc that collects Rincewind and Twoflower from the custody of Tethys the sea-troll. She is about 15 years old with exceptionally dark skin (nearly black). She is a 5th level wizard and a Hydrophobe. She was very worried when she had to capture Rincewind and Twoflower, despite being armed with Ajandurah's Wand of Utter Negativity and says, “Your effected manner of craven cowardice does not fool me Rincewind. I know you to be a wizard of great power and cunning!” To Rincewind this statement seemed to be a strange thing to say but considering how Rincewind had already rescued Twoflower from the combined Thieves, Merchants and Assassins of Ankh-Morpork, defeated the Old Dark God Bel-Shamharoth and escaped the dragons of the Wyrmberg, perhaps her concern was very sensible.
She is a wizard in a field that is generally male because the Krull college of wizards has got the plumbing problem sorted out which prevents Unseen University from recruiting female wizards and women magic-users are commonplace in Krull.