One of the brownie-like spirits of the Highlands. Gruagach has many points in common with this brownie, and in Ulster becomes the "Grogan", according to Wood-Martin, or the "Grogach", according to Lewis Spence. In "Traces of the Elder Faiths in Ireland" (1329: vol.II, p.3), Wood-Martin describes the Grogan as low of stature, hairy, with broad shoulders and very strong, "an unco wee body, terrible strong". Spence in "The Fairy Tradition" (1328: p.101) gives a more detailed account of him.

There is an unusual feature in the story of the Grogach of Ballycastle, where the poor Grogach kills himself from overwork.

It was the custom in the farm to lay out a number of sheaves in the granary overnight for the Grogach to thresh by morning. One morning the farmer left the flail on top of the cornstack and forgot to lay out the usual number of sheaves. The Grogach took it that he was to thresh the whole stack, but in the morning he was found dead on top of the grain. The farmer gave him honourable burial, and he was long mourned.

The Highland Gruagachs were often richly dressed, with golden hair, and watched over the cattle, but the Ulster Grogachs were naked and hairy little men, about four feet in height.

One Ulster grogach, like his Highland counterpart, herded and watched over the cattle. The farmer's daughter, pitying his nakedness, made him a shirt, but he thought that they were trying to lay him, and went away, weeping bitterly.

In another description, the Grogach has a large head and soft body, and seems to have no bones as he comes tumbling down the hillside (1290: p.206, Motifs: F480, F488.i).