Selkies

Recently a grim race of men and women draped in coral, shark teeth and sealskins have overrun Orkney, Shetland and the Faroes. The few occupants of those islands were driven into the ocean or driven through with whalebone swords. Now, they do not gladly speak with humans, and when they do it is always with spear in-hand. They are called selkies or selichs.
Once a peaceful tribe, the selkies roamed the northern seas in their sealshapes, exploring coves, caverns, and canyons. They were also a frequent sight to sailors and beachcombers as they danced together in the waves. What horror of the ocean deep could have driven them permanently ashore and made them so hostile?