In Chloe's house, when she's on the phone with Ella, a drawing (certainly Trixie's work) of a devil can be seen on the fridge.
The school motto is a Latin phrase "Sentio ergo sum", "I feel, therefore I am." This is a deviation of "Cogito ergo sum", putting the emphasis on feelings instead of thought. "Cogito ergo sum", usually translated into English as "I think, therefore I am," is the "first principle" of René Descartes' philosophy. He originally published it in French as "Je pense, donc je suis" in his 1637 Discourse on the Method, so as to reach a wider audience than Latin would have allowed. The dictum is also sometimes referred to as the cogito.
The title is spoken by Lucifer.