The "Three Impossibilities" are a set of tasks left by the very first Miss Cackle. According to legend, completing them undoes any spells cast on that day.
Continues to be strict with Mildred, fearing her "chaotic magical abilities" will lead to disaster. [S4E1] The Three Impossibilities
Involves navigating a complex stone template or grid found in an abandoned tower room. The "Three Impossibilities" are a set of tasks
A second riddle or grid that the girls must solve quickly. [S4E1] The Three Impossibilities