The western wall, with its pointed doorway and gothic atmosphere, was constructed around 1810 not as a place of worship but as a theatrical device, a sham ruin designed to ornament the view from Killua Castle some 625 metres to the northwest. The stones used to build it were robbed from two genuine medieval churches, Killua and Moyagher, dismantled and reassembled to create the impression of venerable decay. Writing in 1867, the historian Cogan was blunt about the deception: the wall was, he said, a modern erection raised "manifestly for the purpose of imparting an appearance of sanctity and antiquity to the scenery."

The irony is that there was a real medieval church here. Dedicated to St. Lucy and associated with a monastery of St. Lua recorded on the 1837 Ordnance Survey map, the site had genuine ecclesiastical history stretching back at least to 1408, when papal records describe one John Owyg, perpetual vicar of Kyllowagh, as too aged and infirm to carry out his duties. The actual fabric of that church was levelled, its dressed stonework either scattered or cannibalised for the folly. Two medieval ogee-headed windows, their hood mouldings intact, were lifted from the original building and reset at first-floor level in the folly's west wall. A narrow chamfered doorway from the medieval church, just 65 centimetres wide, was similarly rebuilt into the same wall beside a much larger 19th-century pointed opening. The work is attributed to Sir Thomas Chapman, who undertook extensive alterations to the Killua Castle estate during the early nineteenth century. The folly was so convincingly done that the 1837 Ordnance Survey mapped it as a genuine church ruin.

Visitors to the graveyard that surrounds the site will find the grass-covered foundations of the original medieval church traceable at the highest point of the enclosure, to the west of the folly. When the antiquarian Oliver Davies visited in 1940, he noted fragments of cut stone scattered about, including part of an octagonal font basin and sections of window jamb, but none of those pieces are now visible above ground. What remains is the folly itself, stripped of its original deception only on close inspection, and below the turf, the faint outline of the church it replaced.