The shrine of the St. Lachtin's arm. Photo by the Metropolitan Museum, New York.
Saint’s relics were an important part of religious practice in medieval Ireland.
The Annals of the Four Masters record that when Palladius first Bishop of Ireland came to Ireland in 430 he brought the relics of Paul and Peter with him.
In this year Pope Celestinus the First sent Palladius to Ireland, to propagate the faith among the Irish, and he landed in the country of Leinster with a company of twelve men. Nathi, son of Garchu, refused to admit him; but, however, he baptized a few persons in Ireland, and three wooden churches were erected by him, namely, Cell Fhine, Teach Na Romhan, and Domhnach Arta. At Cell Fhine he left his books, and a shrine with the relics of Paul and Peter, and many martyrs besides. He left these four in these churches: Augustinus, Benedictus, Silvester, and Solinus. Palladius, on his returning back to Rome (as he did not receive respect in Ireland), contracted a disease in the country of the Cruithnigh, and died thereof.
Saint’s remains were often removed from their graves and placed into specially made shrines. For example in 1162 the Annals record:
The relics of Bishop Maeinenn and of Cummaine Foda were removed from the earth by the clergy of Brenainn, and they were enclosed in a protecting shrine.
Agreements and treaties between kings were sworn on relics. For example in 1152 Ua Lochlainn, King of Cenél nEóġain, and Toirdhealbhach Ua Conchobhair, King of Connacht, swore an oath of fridnedhip under St. Patrick's staff, the Bachall-Isa, and the relics of St. Columcille.
A meeting took place between Ua Lochlainn and Toirdhealbhach Ua Conchobhair at Magh-Ene, where they made friendship under the Staff of Jesus, and under the relics of Colum-Cille.
But when Toirdhealbhach Ua Conchobhair, captured Murchadh Ua Maeleachlainn, King of Meath, in 1143 this was considered a gross violation and the Annals of the Four Masters described in detail the relics on which Ua Conchobhair’s oath had been sworn.
Murchadh Ua Maeleachlainn, King of Meath and its Fortuatha, was taken prisoner by Toirdhealbhach Ua Conchobhair, King of Connaught, while he was under the protection of the relics and guarantees of Ireland. These were they: the altar of Ciaran, with its relics; the shrine of Ciaran, called the Oreineach; the Matha-mor; the abbot and the prior, and two out of every order in the Church; Muireadhach Ua Dubhthaigh, the archbishop, the lord of Connaught; the successor of Patrick, and the Staff of Jesus; the successor of Feichin, and the bell of Feichin; and the Boban of Caeimhghin. All these were between Toirdhealbhach and Murchadh, that there should be no treachery, no guile, no defection of the one from the other, no blinding, no imprisoning, and no circumscribing of Murchadh's territory or land, until his crime should be evident to the sureties, and that they might proclaim him not entitled to protection; however, he was found guilty of no crime, though he was taken. He was set at liberty at the end of a month afterwards, through the interference of his sureties, and he was conveyed by his sureties into Munster; and the kingdom of Meath was given by Toirdhealbhach to his own son, Conchobhar. This capture was effected as follows: a hosting was made by Toirdhealbhach, as if to proceed into Munster; the Connaughtmen, the Conmaicni, and the Ui-Briuin, collected to one place, and Ua Maeleachlainn was taken and conveyed to Dun-mor, together with the hostages of Meath in general; but not the smallest part of Meath was injured on this occasion.