It is a small, unsettling flourish, and it is almost the only ornament that remains on a church otherwise stripped back by centuries of collapse, ivy, and the encroachment of 19th-century grave plots across where the west wall once stood. The two blocked doorways, the stump of an east gable standing isolated from the rest of the structure, and a crossing wall inserted at some point to shorten the building all give the ruin a quietly layered quality, as though several different versions of the same church have been compressed into one.

The beast-head doorway belongs to a late Romanesque tradition, a style characterised by rounded arches, carved stone ornament, and dressed masonry that flourished in Ireland during the late 12th century. Scholars Harold Leask and Brendan Weaver both placed this particular entrance in that period. A 1224 document, quoted by W. Maziere Brady in 1863, provides the earliest written reference to a church at Ballyhay, and the building also appears in the Papal Taxation of 1291, a survey of ecclesiastical properties compiled for Rome. At some later medieval point the structure was substantially reworked: the crossing wall, which divided nave from chancel but was never properly bonded to the side walls, effectively shortened the usable interior. A second doorway in the nave's south wall, with a chamfered and bluntly pointed arch, may once have given access to a sacristy. Above it, on the inner face of the wall, two bearded heads are carved in high relief. By 1615 the nave was already described as ruinous, though the chancel was still in use; by 1694 the building had been abandoned entirely.

The chancel's east gable survives as an overgrown stump, separated from the main body of the ruin, with the splayed sides of a wide central window still readable in the masonry. The crossing wall, though heavily ivy-covered, stands to its full height, and the remains of a tripartite window facing east, one mullion still in place, give some sense of what the later medieval interior once looked like. A stone effigy has been fixed against the inner face of the east gable wall.