Cairns of this kind are prehistoric stone mounds, typically raised over burials, and this one is substantial: roughly 16 metres across at the base and standing about 2.5 metres high. The northern face of the outer kerb still reaches 2 metres, though elsewhere the structure has collapsed and spilled outward, blurring its original edges. A shallow modern depression just west of centre suggests the site has been disturbed at some point, and there may be an entrance passage on the western side, though it remains obscured beneath the fallen material.

The cairn carries a considerable weight of memory and association. In Irish folklore, it was linked to a princess said to have died during a battle between her husband and her father, a narrative recorded in the Irish Folklore Commission's Schools Manuscripts. It was also a site for Lughnasa celebrations, the ancient harvest festival held at the start of August that brought communities to hilltops, lakesides, and other significant landmarks across Ireland. A standing stone roughly 850 metres to the south-south-west in Tavanskea townland was connected to these same festivities, though that stone now lies fallen among forestry. The excavation history adds another layer of uncertainty: Evelyn Philip Shirley, writing in 1879, recorded that a cairn at nearby Knocknaneen had been opened in 1816 and found to contain human bones and an earthen bowl. Since no known cairn survives in Knocknaneen today, that account may well describe the Mullyash cairn itself under an earlier local name.

The site is a designated National Monument and can be reached via forestry roads. It also lies along the Monaghan Way, a signposted walking route, which makes it accessible to anyone already exploring the wider upland landscape. The standing stone in Tavanskea, once a companion to the cairn in local ritual, is worth keeping in mind as you walk; it is there, somewhere in the trees, though you would need to look for it.