A leacht is a low, cairn-like stone structure associated with early Christian devotion, typically used as a station for prayer or as a memorial to a saint, and Inishmurray has several. But this particular one, recorded near the Trahanee enclosure, occupies an uncertain space between archaeology and absence.

The antiquarian W. F. Wakeman, writing in 1893, described the structure in careful detail. He called it an altar, referring to it by the Irish word Altóir, and noted that no one had retained the name of the saint to whom it had been dedicated. He measured it as seventeen feet eight inches in girth at the ground, square in plan, and noted a finial at its summit: a plain upright flagstone, undecorated, bearing no cross or carving of any kind. When a survey team visited the island in 1997 and 1998, they found no trace of it. The working conclusion, offered with appropriate caution, is that Wakeman may have misread his own field notes before going to print, or that the structure genuinely existed and has since been dispersed, its stones absorbed back into the landscape or reused elsewhere. Neither explanation is entirely satisfying, which is perhaps fitting for a site whose dedicatory saint was already forgotten by the time anyone thought to write it down.

Inishmurray itself is an uninhabited island roughly five kilometres off the Sligo shore, accessible by boat from Mullaghmore or Rosses Point in calm conditions. The island retains one of the best-preserved early medieval monastic enclosures in Ireland, and the Trahanee enclosure, near where Wakeman placed his altar, lies within that complex. Visitors exploring the site should be aware that the ground holds many layers of use and reuse, and that the absence of a monument is sometimes as historically telling as its presence.