“St. Dionysius the Areopagite says that evil, introduced by Satan, consists of the following: in mad desire, irrational anger, and unconstrained imagination or fantasy…mad desire, for they [demons] wanted to become like God; irrational anger, for they make haste, not hesitating to kill anyone, to take revenge, and to bring evil upon every one of God’s creations; and unconstrained  imagination, for they fancy themselves to be as God, forgetting that they were created by God.”
(Elder Cleopa+ of Romania quoted in pravoslavie.ru)