Many Anglo-Saxon texts and images attest to a heightened awareness that the body, living and dead, is threatened with being eaten at every stage of its existence before the Last Judgement, after which the damned body will continue to be devoured in perpetuity. These threats may come from creatures of the air (eagles and ravens), creatures that walk on earth's surface (wolves), and creatures that slither and crawl on or beneath the soil, and it is the last of these, the wyrm, that is most continually linked to the condition of both body and soul, before and after Judgement. Wyrm is the generic Anglo-Saxon word used to describe the dragon of Beowulf, the smeawyrmas that invade the living body in the leechbooks, and the corpse-devouring moldwyrmas of the Soul and Body poems, as well as other creatures, some of which appear, at first at least, to have little in common.

Wyrm is such a broad category that, used loosely, it risks becoming meaningless: it includes scorpions and spiders as well as dragons, snakes, maggots, lice and fleas. Neville calls the Anglo-Saxons ‘imprecise’ in their use of wyrm, and she draws attention to Isidore of Seville's broad use of serpens and vermis, implying that Anglo-Saxon ‘imprecision’ has its origin in the learned tradition. But this fails to take into account the ubiquity of these creatures in Anglo-Saxon culture. Wyrmas partake of some common qualities with which a Linnaean system of classification fails to cope, including poisonousness, an intimate relationship with human flesh, a taste for the same, an uncanny way of moving (creopende), the ability to disappear underground and a closeness to the dead.