Máel Ruain was an abbot-bishop in Dublin. His real name is unknown; Máel Ruain was his monastic name, from Old Irish máel meaning "one who is tonsured" and Ruain meaning "of Rúadán," so he likely started at the monastery of St. Rúadán. Some credit him with bringing to the Culdees the same kind of organization that Chrodegang of Metz brought to the continent with his Rule.
Máel Ruain founded the monastery of Tallaght, a few miles south-west of Dublin. The Book of Leinster (compiled about 1160) includes a reference to the land at Tallaght being given to Ruain from the king in 774. It had round towers designed as bell towers that doubled as sites for relics he brought from the continent of Saints Peter and Paul, along with hair from the Virgin Mary. It became an important center of learning and produced two early martyrologies, one about Máel Ruain himself.
The rule at Tallaght was similar to the Rule of Chrodegang. A 1911 book, The Monastery of Tallaght, published by the Royal Irish Academy, presents information from historical documents about Tallaght and describes their shared asceticism thusly:
Not a drop of beer was drunk in Tallaght in Maelruain’s [sic] lifetime. When his monks used to go anywhere else, they used not to drink a drop of beer in Tir Cualann, whomsoever they might happen to meet. However, when they went a long distance, in that case they were allowed to drink. Nor a morsel of meat was eaten in Tallaght in his lifetime [unless] it were a deer or a wild swine. What meat there was [at Tallaght was served to] the guests.
Máel Ruain died in 792. The monastery survived viking attacks, but not the Norman Invasion. In the 12th century it was attached to the Archdiocese of Dublin. It went through a few changes of hands, but only one tower remains of the original structure. Today it is the site of St. Máelruain’s Church of Ireland, built in 1829.
While we're in Ireland, we should look at other records, such as the Book of Leinster...next time.