Somewhere on that famously austere island, just above the opening to a cistern, there once stood a small upright slab. Whether it was a deliberately shaped stone cross or simply a rough piece of rock pressed into devotional service was never entirely certain. It has since vanished entirely, and no visible remains survive.

The slab was recorded in 1996 by archaeologists A. O'Sullivan and J. Sheehan as part of their survey of the Iveragh Peninsula, at which point it measured 0.77 metres tall, 0.36 metres wide, and 0.13 metres thick. Its position beside a cistern, a water-storage feature cut or built into the rock to collect rainwater for the monks who lived here from around the sixth century onwards, suggests it may have marked or sanctified that practical resource. Skellig Michael's monastic settlement, a UNESCO World Heritage Site, is already well documented for its beehive-shaped dry-stone cells, its oratories, and the vertiginous stairways carved into the cliff. This small slab occupied a quieter corner of that record, notable precisely because its identity was uncertain even when it could still be seen. By the time researchers returned to confirm or revise the description, it was gone.