Set into the wall is a recumbent rectangular slab, just over two metres long, whose surface is crowded with imagery: a cross bearing fleur-de-lis terminals grows out of a crown of thorns and is surrounded by the Instruments of the Passion, the whip, hammer, nails, ladder, and pincers that feature in medieval and early modern devotional iconography as symbols of Christ's suffering. At the base of the cross-shaft, resting on a pillar-base form, sits a skull and crossbones accompanied by an abbreviated Latin phrase, moriemur omnes, meaning roughly "we shall all die." The tomb niche itself is lined with 17th-century stucco work of considerable elaboration: the soffit carries four angels set among the sun, moon, and stars; the east wall retains the remains of a crucifixion scene; and the west wall bears a coat of arms, badly eroded now but once presumably identifying the family whose monument this was.

The slab commemorates Nicolaus O Kearny, described in the Latin inscription running around its edge in Black Letter script as a burgess and citizen of the archiepiscopal city of Cashel, and his wife Hellena Raggett, daughter of one Thomas of Kilkenny. The inscription, transcribed by FitzGerald in the early 1900s, is badly worn and incomplete in places; the date of Nicolaus's death is no longer legible, though Hellena's is recorded as the 23rd of September, year uncertain. The Raggett family connection to Kilkenny and the formal civic title given to Nicolaus suggest a household of some standing in the town that grew around the rock. A front panel, repaired at some point, runs along the base of the monument on a chamfered plinth and carries a centrally placed IHS monogram, a widely used Christogram, with a Latin cross rising from the bar of the H and a heart pierced by three nails beneath it. One side of the upper slab is broken, and much of the inscribed Latin has been lost to erosion, leaving FitzGerald's early transcription as the most complete record of what it once said.