Selkie

Selkies are seal creatures that can shed their skin once on land to become human. The mythology comes from Faroese, Irish and Scottish folklore although there are several creature like the shape-shifting selkies in other folklore around the world. The word comes from the old English seolh that was then taken by the Scottish selich, meaning seal. The legends have been found to originate in the Orkney and Shetland islands of Scotland.

 The selkie's seal skin is what holds their power and if stolen and hidden or burnt they would be under your power, prevented from going back to their water home, they are also like finger prints, unique to each selkie, only one particular skin would work with that one particular selkie, the magic of the skin wouldn't make anyone turn in to a seal if put on. That is why they are so presious. There are a few theories about what happens when the skin is destroyed. they say either the selkie dies or they are doomed to be human until they die, always longing to go back to the ocean but never being able to.
  The males are said to be extremely handsome and with great seductive powers in their human form, drawing women who typically aren't happy with their lives and/or are waiting for their husbands to return from sea. It is said that if a women wanted to make contact with a selkie she had to cry seven tears into the ocean.

  The females also being beautiful and seductive, where said to make great wives. Even having children with their human husbands. Males would have to lure one in and steal her seal skin, this would then force the selkie into marriage.

  The stories and folklore of the selkies are normally romantic tragedies because even though their love of a mortal may be strong, the pull of the ocean is always stronger. Either the stealing of the skins and the force to stay on land or the lover not knowing that they where selkies and waking up one day to find that their love had changed into a seal would also force tragedy into their tales.
 A selkie also couldn't have contact with the same human once left for seven years, unless said human stole their skins. Although their are a few stories where the selkie female is happy married with a fisherman. This tale always ends with the wife having to change back into her seal form to save her husband from the sea and then never being able to go back to her home on land.

  There are two types of selkie. Ones from the seelie court (which is said to be the fae that are more on the light side, often helping those in need, although when bored can make lots of trouble, nothing ending in great harm and not into hating humans) are good natured, shy and would help those in need, they are hard to anger but can do if enough is done to them. Were as the selkies from the unseelie court (being the fae of darker things and hating just about everything especially humans, they are out to harm) where said to be the harbingers of storms, one that would sink ships as revenge for the harm of kin.