Humans, and even monsters, affected by the daemonblight turn into daemons. While most daemon-turned humans go berserk, some retain their sense of reason. The form that a creature affected by daemonblight will assume is hard to predict, but humans will often turn into lizards or werewolves. In actuality, daemonblight does not exist, being a term coined by the Abbey since anyone can become a daemon if the "impurity", or darkness, in a human heart overflows them. If such information got to the public, it would result in mass hysteria, as well as mass transformations into daemons. Opening of the gate from ten years prior to the events of the story resulted in humans being able to see daemons. There exist various species of daemons, such as therions, who feed on others to gain strength, and yaksha (夜叉 yasha?), also known as war daemons.
According to the malak Zui Fuu, who resides in The Heavenly Steppes, the existence of daemons is the result of a curse that was imposed upon humans and malakhim, seraphim who left the heavenly realm to live side by side with humans, by the seraphim who remained in the heavenly realm to ensure that coexistence would never happen.
- Daemon derives from the Latin daemon, meaning "guardian spirit", or the Ancient Greek δαίμων (daímōn) meaning "protective spirit", or more ecclesiastically, "evil spirit".