"The Moon-Bog" by H. P. Lovecraft

THE MOON-BOG was first published in the June 1926 issue of Weird Tales.
The story is narrated by a friend of Denys Barry, an American who purchases an ancient estate near a bog in Ireland with the intent of draining the swamp and modernizing the land. Despite warnings from the superstitious locals about ancient legends tied to the bog, Barry proceeds with his project, disturbing the resting place of strange, long-forgotten beings.