When Ciaran was planting the first post to mark out the site of the Cathair of Clonmacnoise, Diarmaid Mac Cearbhaill, who happened to be present with a few of his companions, helped the saint with his own hands to fix the post in the earth. "Though your companions to-day are few," said Ciaran, "to-morrow thou shalt be High King of Erin." This prophecy, like many others, helped to fulfil itself. One of Diarmaid's companions, Maelmor,[212] his foster brother, overheard the saint's word; and knowing that he was a man of God, he resolved to help in carrying it out. King Tuathal Maelgarbh, great grandson of Niall the Great, had set a price on Diarmaid's head, or rather on his heart, if brought to him in person; so Diarmaid was forced to hide himself and live in the deserts and bogs around Clonmacnoise. There he met the saint, and not only aided him to build his monastery, as stated above, but in reverence to the saint he placed his own hand beneath that of Ciaran in fixing the first pole. Now, Maelmor hearing the prediction, with Diarmaid's reluctant consent, took his fleet black horse, and a whelp's heart besprinkled with blood on the point of his spear, and rode post haste to a place called Greallach Eillte in Meath, where the king with his nobles happened to be at the time. Seeing the stranger riding post to the king with the bloody heart on his spear, all made way for him, for they, like the king himself, thought it was the heart of Diarmaid, which he was going to present to the king. But instead of Diarmaid's heart, Maelmor gave the monarch a fatal thrust with his spear, which killed him on the spot. Maelmor was immediately set upon by the royal guards and hewn to pieces. But his purpose was achieved--Diarmaid MacCearbhaill was the nearest heir to the throne, and was immediately proclaimed king without opposition. During his reign he was, as might be expected, a great patron and benefactor of Clonmacnoise, and although there is good reason to believe that he still kept Druids[213] and soothsayers in his palace, he gave that monastery large grants of land, and subjected to its authority no less than one hundred of the small churches in its neighbourhood. Such was the origin of the Diocese of Clonmacnoise, which after many vicissitudes is now united to that of Ardagh.[214] St. Ciaran lived only four months after founding his monastery and little church--the Eclais Beg--on the banks of the Shannon. The same accurate writer of his life states with great precision that his death came upon him in the thirty-third year of his age, on the fifth of the Ides (the 9th) of September, on a Saturday, the fifteenth day of the moon. These data mark the year A.D. 544 (not 549), as the year of the saint's death. It was also the year in which King Diarmaid ascended the throne, and which brought with it a great plague that proved fatal to many of the saints of Erin, as well as to Ciaran himself.