The Lives of Ciarán, both Latin and Irish, differ in their details but seem to derive from a common archetype of some antiquity, written by a member of the community of Saigir when it was still flourishing. They portray him as a saint in the primitive mould, a cross between John the Baptist and Francis of Assisi: clad in animal skins, subsisting on the simplest food, and befriending the animals of the forest – ‘Now a boar, a fox, a badger, a wolf, and a deer with her fawn came humbly to him and served him in all obedience’. He preached within the territory of Osraige, displaying the usual manifestations of divine power.
A gloss in the Martyrology of Óengus (qv) (fl. c.830) mentions the existence at Saigir of an illuminated manuscript known as ‘Imirche Ciaráin’: ‘that wonderful manuscript, namely Ciarán's “journey”, with its many various illustrations, and this book still remains at Seir’; this suggests that Ciarán came to be associated with voyage literature: he is mentioned in the Irish litany of pilgrim saints. He is described as ‘first-born of the saints of Ireland’ in the Martyrology of Óengus, where his feast-day is given as 5 March.