The Aleister Crowley Arc is a story arc in Shinyaku Toaru Majutsu no Index, covered in Shinyaku Toaru Majutsu no Index Volume 18.
Following their encounter with Aleister Crowley, Tsuchimikado Motoharu and Karasuma Fran seek Kamijou Touma's help in escaping from Academy City. However when Tsuchimikado Maika is struck by Aleister's magic, the group are forced to break into the Windowless Building to find a way to safely remove it.[1] While ascending the massive structure, Touma is shown a series of visions, detailing Aleister's past, his time with the Golden Dawn, and the reasons behind his battle to destroy all magic.[2][3] At the end of the climb, a confrontation with Aleister Crowley himself awaits.[4]