Small churches were established in Termon and Kilrush, on Cruit Island and possibly elsewhere along the coast of West Donegal and Ancient Fermanagh. Priests based at the monastery of Inish Caoil said Mass in these churches and cared for the spiritual needs of the small scattered population along the Rosses' seaboard. That seaboard or headland belonged the O' beolain family were hereditary lay abbots of Applecross, a monastery on the west coast of Scotland opposite the Gaelic island of Raasay-one of the Inner Herbridean Islands, to the East is the Scottish mainland and to the West is The Isle of Skye. The Norse name "Raasay" means Isle of the (Roe) or Red Deer. Saint Moluag of Cromarty was of Irish/Pictish stock which could explain why he was so successful in spreading the gospel in Raasay and securing a foothold in North Skye, both Pictish centres, i.e, Applecross, Cashel, Cromarty, Raasay, Isle of Cumbrae, Largs, Crom Cruach, Whithorn, Fearn.

Between 545 and 562 Saint Columba founded more monastic institutions including Durrow, Kells, Arran, Boyle, Swords, Raphoe, Tory Island, Glencolumbkille, and Drumcliff. The comharb, or successor, to St.Conall Caol, ruled the monastery of Inish Caoil. This office of comharb, or abbot was dynastic, which meant that holder of the post invariably belonged to the local ruling family. He was chosen from the muinntir or kin, of the founder of the monastery, a practice which gave rise to widespread abuse in time. The concept of muinntir was similar to the old Roman gens, in that it consisted of a group of families who claimed descent from a common ancestor. (Clan).

It was custom that the muinntir of the founder of a monastery would donate lands to that monastery, the management of these lands would in time be entrusted to a particular sept who would pay the comharb a fee for the use of the land. The steward of the lands was called the erenagh (airchiennach). The church lands were called erenagh lands.

The Síl Ciarain Ua nEchach were located in Airtheraib in Ulster, according to the Book of Lecan and Book of Ballymote. About the 5th century, a northern tribe moved into East Galway; they were said to be descended from Colla dá Críoch (one of the Three Collas). According to the Munster Annals, Síl n-Anmcadha Ó Dúnadhaigh (O'Downey) were chiefs of Síl Anmchada up to the 11th/12th? century, prior to the rise of the Ó Madudháin (O'Madden) sept. The Ua Braonain of Siol Anmchadha, closely related to the O'Maddens were located in the barony of Longford, county Galway. As such they were a branch of the Uí Maine. The eponymous ancestor of the O'Maddens is given as Madúdhan, a chieftain of Síl n-Anmcadha who was slain in 1008. In 1023, the Termon of Cluain-mic-Nois was plundered by Gadhra, son of Dunadhach, and carried off many hundred cows from thence.

In 1609 during the Ulster Inquisitions a jury composed of representatives of the old Gaelic families of Tir Chonaill reported "And further, the said jurors do, say and present that in ancient times there were divers lands given by temporal lords to saints or holy men in the said county (Donegal) for celebrating divine service and praying for their soul's health, and the saints or holy men, dedicating themselves to prayer and the service of God, did, for their better ease, ordain and constitute several herenaghs to manure and occupy those lands, and the principal of the sept was named the herenagh who successively did enjoy those lands, yielding and paying certain rents to the saints." The monastery of St.Crona possessed its own landed property and over the course of time these became known as termon or erenagh lands.

Both Breffnys anciently formed part of Connaught, but the new county was incorporated with Ulster. The O'Reillys were at this time a warlike sept, particularly distinguished for their cavalry, and not living in towns, but in small castles scattered over the country... Two of the boroughs that were created and received these grants were Cavan and Belturbet (Enniskillen), and the other 250 acres were to be given to a third town, to be erected midway between Kells and Cavan, on a site to be chosen by the commissioners appointed to settle the plantation; this place was Virginia or Virginia through Louisiana. This being completed, the king resolved on the new plantation of Ulster, in which the plan for the division of this county was as follows: -- the termon, or church lands, in the ancient division, were 140 poles, or about 3500 acres, which the king reserved for the bishop of Kilmore; for the glebes of the incumbents of the parishes to be erected were allotted 100 poles, or 2500 acres; and the monastery land was found to consist of 20 poles, or 500 acres. Census 1659

When we come to define the exact lands that were granted to him, we must quote from a later Inquisition, for the account of the termon and erenagh lands of the 1609 Inquisition is amplified by a more explicit list given in Pat. Rolls 18 Jas. I (Mar. 1620-Mar. 1621). Termonfechin, near Drogheda, Co. Louth. The documents date from 1700 and 1786-1880 (with many gaps), and include a letter from Sir Henry Tichborne about the Primate's title to the tithes of Termonfechin, 1700, specifications, a plan and correspondence about alterations to the church, 1862, and a c.1870 schedule of formal documents relating to buildings over the period 1744-1862. Termonmaguirke, near Omagh, Co. Tyrone. The papers run from 1730 to 1966 (with many gaps), and include a petition to build a new church at Sixmilecross, 1733, a book containing a list of the inhabitants of the parish of `Temont', 1780, papers about enlarging Termon Church, 1861, and a c.1870 schedule of formal documents relating to buildings over the period 1733-1861.

The diocese of Ossory, "Ireland's oldest bishopric", was probably co-terminus with the ancient kingdom of Ossory. Its present boundaries were set at the synod of Rathbreasail. It includes most of the county of Kilkenny (except for the parishes of Graiguenamangh and Paulstown), part of Co. Laois and the “island” parish of Seir Kieran in Co. Offaly. The coming of the Cistercians to Jerpoint probably around 1160 and to Kilkenny had already signaled the passing of the old Celtic order, and soon the Canons Regular of St. Augustine were firmly installed in Saighir Kieran and Fertagh and had set up new foundations in Aghmacart, St. John's, Kilkenny, Kells and Inistioge; their sisters were in the nunnery of Kilculiheen. The transfer of the Cathedral from Aghaboe to Kilkenny in the last decade of the twelfth century, the foundation of a cathedral chapter and the establishment of a parish system through the system of tithes introduced by the Anglo-Normans radically transformed the ecclesiastical organization of the diocese. More than half of the new parishes were in the hands of the religious, while the rest were run by the secular clergy - mostly the dean and chapter of St. Canice's. A few were in the hands of lay patrons. In the 13th century the Dominicans came to Aghaboe, the Black Abbey in Kilkenny and Rosbercon. Because of their importance in the diocese the suppression of the monasteries in the wake of the reformation led to enormous changes. The Suir was a major traffic artery and the monastery was not therefore immune from the commercial world outside its walls. During the 1220s Inislounaght became heavily involved in the ‘conspiracy of Mellifont’ (1216-1228) and the abbey became a centre of rebellion against the Cistercian General Chapter. Abbeyleix, Laois, the Mother house of Baltinglass was founded by Connor O’More in 1183 although the first monks did not arrive from Baltinglass until a yeare later. The site was on the banks of the River Nore, over thirty miles upstream from Jerpoint.

St. Kieran (Ciaran) of Saighir built himself a cell in a place encompassed with woods, near the water of Fuaran- an early Irish bishop is also called Ciarán Saighir (the Elder) to distinguish him from Saint Ciarán of Clonmacnoise. St. Patrick and St. Kieran of Saighir met many times. In particular, they met at the Rock of Cashel when Patrick started his mission in Munster (Ely).

Saint Ciarán (or Saint Kieran) is the name of many Irish saints. St. Kieran of Clonmacnoise is founder of Seir-Kieran, Kings County (about A.D. 450), and also of the See of Ossory. Clonmacnoise is situated on the Shannon, about half way between Athlone and Banagher, in Co. Offaly, Ireland within Meath or Tara. St. Kieran (Ciaran) of Clonmacnoise, also known as St. Kieran the Younger, was born around 512 AD in Connacht, Ireland, a town located in the northern part of County Roscommon. Kieran continued his education at the monastery of Clonard, which was led by St. Finnian. Tighernach, the most accurate and most ancient prose chronicler of the northern nations, belongs to Clonmacnoise, and probably also Dicuil (q.v), the world-famed geographer. Clonmacnoise, one of the most remarkable of the ancient schools of Erin was founded by St. Ciarán surnamed Mac an Tsair, or "Son of the Carpenter".