St Kilian is traditionally believed to have been born in the first half of the seventh century, possibly about 640 AD, in Cloughbally, a short distance south-east of his Holy Well. He belonged to a branch of the Gailenga people, who lived and ruled in East Cavan and North Meath. In the twelfth century much of the territory was over-run and became part of the Kingdom of Breifne, ruled by the O'Rourkes and the O'Reillys. The cult of St. Kilian was long established when the new rulers of the region took it over and became protectors of St. Kilian's church, Teampall Cheallaigh, and of his Holy Well, Tobar Cheallacháin, in what later became the parish of Mullagh.
Kilian is believed to have received his religious training at the monastery in Rosscarbery, Co. Cork founded by St. Fachtna in the fourth century. St. Kilian later founded his own monastery off Kilmakilloge harbour in the Kenmare area, where he trained his fellow monks and laid plans for one of the greatest pilgrimages ever undertaken from the shores of Ireland. From Kilmakilloge harbour, Kilian and his twelve companions , their heads tonsured in the traditional fashion of the Irish monks, set sail on their mission in a hide-covered boat. Their journey finally brought them to Rome where Pope Conan directed them to Germany and to the province of Franconia, where they set up their head quarters at Wurzburg in the year 686. All around, the countryside was pagan, with perhaps a few pockets of Christians here and there. The influence of the earlier Barbarian invasion was still felt.
Kilian was a frontier man, a pioneer whose mission was to extend the frontiers, like St. Patrick in Ireland and St. Colmcille in Scotland. His mission was a huge success and in a short time Duke Gosbert, ruler of the locality, was converted to Christianity and, following his example, most of his people became Christians. A few years later, rumours of low standards in high places began to circulate and reached the ears of Kilian. Duke Gosbert was having an affair with his brother's wife Geilana. Kilian was quick to denounce the scandal. Geilana was furious at his interference and secretly hired two assassins to murder Kilian and his two companions, Colman and Totnan, while Gosbert was away hunting. The three Irishmen were at prayer when they were set upon. Their heads were cut off, their bodies secretly buried. This was in 689AD. It was not until much later that their burial place was discovered , following a public fast by the people of Wurzburg.
Kilian's death was not recorded in his homeland until the ninth century. It was entered in the Martyrology of Tallaght, among the Irish saints mentioned there. From the time that his relics were first enshrined in the cathedral of Wurzburg his cult spread throughout Central Europe, ultimately to Italy, Great Britain and further afield. It spread as a popular devotion among ordinary people. The wine growers of Franconia took it up and he became their patron; he also became the patron of shepherds of Thuringia and Italy. They prayed to him for the cure of many ailments, in particularly diseases of the eye, rheumatism and gout. Thousands began to flock to Wurzburg to his shrine. Later on, Christian McCarthy, Abbot of the Irish Monastery in Regensburg, applied to the Bishop of Wurzburg to build a hostel to accommodate pilgrims to Kilian's shrine.
The earliest documented reference to the dedication of the parish of Mullagh to St. Kilian is in a letter in the Archives of Propaganda in Rome dated 27 September 1715, supporting the nomination of Michael Smith as Bishop of Kilmore, signed by twenty seven parish priests including Edmund Gargan, ‘pastor of the Church of St. Kilian of Mullagh’. Edmund Gargan became pastor of Mullagh in 1710, so the parish of Mullagh certainly was dedicated to St. Kilian at least from 1710, and possibly much earlier. J. O’Donovan also wrote, ‘the parish of Mullagh is dedicated according to tradition, to St. Kellach...his church is called Teampall Keallaigh and anglicized Temple Kelly, from which it will appear probable that his real name is Ceallach’. The present parish church of Mullagh, opened in 1858, is dedicated to St. Kilian. For many years pilgrims from Wurzburg and indeed from other parts of Germany have visited Mullagh in search of their spiritual roots. The first official pilgrimage from the Diocese of Wurzburg came in 1987. Since then a strong bond has been established between the birthplace of St. Kilian and the place of his death. In July 1989 a pilgrimage from Mullagh parish led by the Most Reverend Francis MacKiernan, Bishop of Kilmore joined an Armagh pilgrimage to Wurzburg led by Cardinal Tomás O Fiaich to mark the thirteenth centenary of St. Kilian’s martyrdom. In August Bishop Bauer led a Wurzburg pilgrimage to Mullagh then celebrating the same centenary year. Since then the pilgrim links have strengthened and to accommodate this devotion to St. Kilian and to provide for it a focal point, the St. Kilian Heritage Centre – Áras Chillian – was built with support from the local Community, the Diocese of Wurzburg and the International Fund for Ireland. The Centre was opened by Mary Robinson, President of Ireland, in 1995.