Olioll Olum, King of Munster (O. Olum, King of Ireland) became King of Munster
by his wife. He was the first of this line named in the Regal Roll to be King
of both Munsters. For before him, there were two septs that were alternately
Kings of Munster, until this Olioll married Sabina, daughter of the Mornarch
Conn of the Hundred Battles, and widow of Mac Niadh, Chief of the other sept
of Darin, descended from Ithe, and by whom she had one son named Lughaidh,
commonly called "Luy Maccon". Lughaidh, when he came to man's age, demanded
from Olioll his stepfather, the benefit of the agreement formerly made between
their ancestors, which Olioll not only refused to grant, but he also banished
Maccon out of Ireland. Maccon retired to Scotland where, among his many
friends and relations, he soon collected a strong party, returned with them to
Ireland, and with the help and assistance of the rest of his scept, he made
war on Olioll. On Olioll's side was Olioll's brother-in-law, Art-Ean-Fhear,
then Monarch of Ireland who came with a good army. They fought the great
battle of Magh Mucromha (or Muckgrove), near athenry, where the Monarch Art,
together with seven of Plioll's nine sons, by Sabina, lost their lives and
their army was totally defeated and routed. By this great victory Maccon not
only recovered his right to the Kingdom of Munster, but the Monarchy also,
wherein he maintained himself for 30 years, leaving the Kingdom of Munster to
his stepfather Oliool Olum, undisturbed. After the battle, Olioll, having but
two sons left alive, namely Cormac-Cas and Cian, and being very old, settled
his kingdom upon Cormac, the elder son of the two. But soon after being
informed that Owen Mo'r, his eldest son (who was slain in the Battle of Magh
Mucromha),had, by a Druid's daughter issue, named Feach (Fiacha Maolleathan),
born after him Cormac's son and their posterity to continue by turns. This
arrangement was observed by them for many generations, sometimes dividing the
Kingdom between them, by the name of South or North Munster, or Desmond and
Thomond.