Look more carefully and it becomes something genuinely odd: a stone inscribed in two entirely different writing systems, one Irish, one Norse, saying more or less the same thing about the same man. It is not a common thing to find.

The stone was found in 1916, built into the fabric of the wall surrounding the cathedral enclosure, presumably reused as ordinary building material at some forgotten point. Measuring roughly 89 by 46 centimetres, it carries a runic inscription on its face, the script used by Viking Age Scandinavians, reading THURGRIM RISTI KRUS THINA, meaning "Thorgrim raised this cross". On the side, a damaged ogham inscription, the ancient Irish script of notched lines along a central stem, can be restored with reasonable confidence as BENDACHT FOR TOROQRIM, or "a blessing on Thorgrim". The scholar Damian McManus classifies the ogham here as scholastic, meaning it was written by someone working from learned tradition rather than as a living everyday script, and dates it to after the seventh century on those grounds. The higher portion of the stone has been broken off, and scholar Peter Harbison has suggested it may originally have formed part of a high cross shaft. The back bears what appears to be a carved crucifixion scene, with traces of a second panel above it. The Thorgrim in question is almost certainly Thorgrím Furcap, who came to Killaloe in the winter of 1102 to 1103 as part of the retinue of Magnús Barelegs, King of Norway, who had arrived in the town in 1102. That a Norse visitor, or someone commemorating him, would commission an inscription in both runic and ogham scripts in an Irish ecclesiastical setting suggests a moment of deliberate cultural meeting rather than simple conquest or passage.