someone brought up Harry Potter. well, Albus Dumbledore, headmaster of Hogwart's School of Witchcraft and Wizardry, has this on his letterhead:

Order of Merlin, First Class, Grand Sorc., Chf. Warlock,
Supreme Mugwump, International Confed. of Wizards

now, confederation just didn't seem right, applied to wizards... BUT...

a league, an alliance (between persons or states; in mod. use only the latter). Formerly also in a bad sense, Conspiracy. [emphasis added]

... therefore and QED: a conspiracy of wizards