It is whale bone, a material so unexpected in a piece of medieval ecclesiastical architecture that it tends to stop people mid-step. The window itself is a slender round-headed lancet, 2.4 metres high and barely 21 centimetres wide, set in a splayed embrasure that opens the light inward. That a beam of whale bone was chosen to cap it is unexplained, but it is far from the only curiosity the building holds.

The church sits on a bedrock bluff above the Easkey River in the village of the same name, enclosed on its south and west sides by an L-shaped walled graveyard. It appears in the Ecclesiastical Taxation of Ireland of 1306 under the name Imelackiskel, valued then at five marks. The lancet windows are thought to date from the 13th century, while a hood moulding over the south doorway, which frames the entrance with carved stone decoration, belongs to the 15th or 16th century. That moulding once incorporated three carved stone heads, including one at the apex of the arch depicting a mitred bishop. The antiquarian William Frederick Wakeman recorded them in a drawing made in 1879, by which point the heads were already the most arresting feature of an otherwise plain rural church. When a graveyard survey was conducted in 2015 and 2016, several displaced fragments of the moulding were recovered from within the graveyard, among them one of the carved heads, badly damaged, and the bishop's head, which had been found separately some years earlier with its decorative mitre band still legible in the stone. Wakeman's 1879 drawing also shows a ringed cross at the apex of the west gable, noted independently by Wood-Martin in 1882 as a remarkable cross on the old church at Easkey. Two fragments of that cross, with rope-chord decoration on the outer edge of the cross circle, were found in 2015 at the base of the west gable interior.

The interior is grass-covered and crowded with grave slabs, three table tombs, and low uninscribed markers; some of the slabs appear to be 18th century in design, though their inscriptions are no longer legible. A 19th-century grave in the south-east corner presses up against the east window, and the surrounding walls have been covered in cement plaster to a height of about 1.75 metres, a practical intervention that sits awkwardly against the older fabric. Conservation work was carried out at the site in 2021 and 2022 under the Community Monument Fund in partnership with Sligo County Council, stabilising what remains of a building that has been accumulating layers, literal and historical, for the better part of seven centuries.