From Irish Climbing Wiki
The long easy-angled south ridge of Slieve Muck has a number of small broken shale outcrops, On the largest of these is Arete Climb 27m VD (P. Gribbon, T. Nevin, B. White. 4/10/53.) which follows the crest of the buttress, and there is much bouldering to be had if you happen to be passing by.