When Ilus is subject to a major storm, such as the one that hit after the reactors blew up in Cibola Burn, slugs which appear to have been hibernating underneath the surface, come to the surface. These slugs, at first, seem harmless but, when touched, humans quickly succumb to a paralyzing slime that coats the slug's body, this can lead to death.

After the threat of Death slugs has been realized, the people of Ilus carefully work in groups with a dedicated person on slug watch.