The Adhene, also known as the Manx fairies, are said to be fallen angels cast from Heaven, but too good for Hell. They could be benevolent, but are mischievous towards humans, taking babies when they choose, although their powers are said to not be more effective than humans on an errand of mercy. When visible, they are said to be the size of a child, fish at sea, and herd cattle on the hills. They know where to fish apparently when they hear fairies making storage barrels in the caves.
(Source: Rose, Carol. Spirits, Fairies, Leprechauns, and Goblins: An Encyclopedia. 1998.)