The Illusionist Castle was one of the many dormitories founded after Brakebills University was established in 1763. Located at the edge of the forest surrounding the school, the castle was difficult to find unless students had an illusionist-type discipline.
After Quentin Coldwater made it into the Physical Kids' Cottage after his assignment to Physical Magic, he asked Eliot Waugh if all Disciplines at Brakebills had clubhouses. The Illusionists Castle was one of the facilities Waugh mentioned, but he explained that only Illusionists knew where it was and students had to find it to get in.
Plum Purchas was assigned to the castle after her Discipline was determined as camouflage magic. She described it as "delicate and gossamer and very Neuschwanstein", and considered it better than the Cottage the Physical Kids were housed in. Whenever the Illusionists had parties, the castle could be made to twinkle and float into the air slightly, connected to the ground only by a rickety, railing-less staircase which people feel off of when they were drunk.
- According to Plum Purchas, the Illusionist Castle is similar the castle on the Disney logo.