Cardinal Strauss' quote, "And when you write of us... and you will write of us... May I ask one thing? Do so gently." is a paraphrase from Tea and Sympathy (1956), in which Deborah Kerr's character says, "Years from now, when you talk of this... and you will... be kind."
Hans Zimmer's score directly quotes passages from Goblin's score for classic Italian horror film Suspiria (1977) on several occasions related to the Illuminati.