A hole in the Veil between this world and that of magic. When the Veil tears and a rift forms, demons pour out into the world and attack any they find.

[He moves away from her to cautiously look outside their hiding place, though he doesn't feel much better at the lack of demons there.]

If they're spreading out here, they'll attack all that they can find. I should do what I can to warn others and protect them, since I can't stop them directly.