Castledermot in County Kildare is already well known for its remarkable concentration of early medieval stonework, including two high crosses and a Romanesque doorway. Slightly less celebrated is a fragmentary limestone slab that survives from the same monastic complex, its surface carrying a design that sits somewhere between sacred geometry and decorative ornament: an incised eight-armed fleur-de-lys cross.

What survives is the upper portion of a tapering slab, measuring 0.88 metres in length and between 0.53 and 0.66 metres in width, with a thickness of 0.16 metres. The taper suggests it was once a grave marker or upright memorial stone, with the lower section likely set into the ground. The cross type is unusual. A fleur-de-lys cross uses the stylised lily motif, more familiar from heraldry and decorative arts, to form the terminals of each arm. Here, eight arms radiate outward rather than the conventional four, producing a form that has something of the compass rose or the wheel cross about it. The incised technique, where the design is cut into the stone surface rather than carved in relief, was common in early Irish ecclesiastical stonework, and Castledermot's monastic site, founded according to tradition by Saint Diarmait in the ninth century, produced several such carved pieces. The slab was recorded and described by Bradley and colleagues in their 1986 survey of the area.