The record on Coflein says this 1.8m high mound is now part of 'domestic garden'.
[I examined] a large cairn on the opposite side of the River Ogwen, about a mile south of the village of Llandegai and close to the back of the keeper's house at Llys-y-gwynt. It was called "Carnedd Howel" from the popular belief that it was the resting place of a prince of that name: but it is hardly necessary to say that these associations of prehistoric burial-places with historical personages are generally mythical; they date probably from a comparatively recent period, when history itself had become somewhat legendary, and when past events had become jumbled together in the traditions of the people.
..An old man of 80, named Robert Roberts, told me that, as a boy, he was much afraid of passing here by night, as he had often seen lights dancing about on the Carnedd.
From p309 of
On the Opening of Two Cairns Near Bangor, North Wales
A. Lane Fox
The Journal of the Ethnological Society of London (1869-1870), Vol. 2, No. 3. (1870), pp. 306-324.