Daemonblight (業魔病 Goumabyou?, "Resentful Demon Disease") is the name assigned to the "disease" that results in humans transforming into daemons in Tales of Berseria. It began spreading rapidly after the Opening.
In actuality, "daemonblight" is the veiled term invented by the Abbey to refer to the corruption of humans due to malevolence, resulting in daemonic transformation. Malevolence has always existed and turned humans into daemons; however, it was the Opening that allowed for humans to see these daemons, fueling the myth of daemonblight and its sudden appearance in the world. This information is not common knowledge, however, as only high-rank exorcists and malakhim know of this fact; for the latter, the subject is taboo and not meant to spoken of. Eizen comes forward with this revelation when the group returns from Haria, having witnessed an outbreak of daemonblight in the village upon seizing the therion held within the Palamides Temple. In addition, it is later revealed that therions are daemon-eating daemons who actually consume malevolence, keeping the balance stable through seven earthpulse points scattered across the world.