(Oh my goodness, I LOVE this idea! C: Maybe Kelpie could be captured/found by one of the insane goddesses and be corrupted and turn evil! >:3 EVIL KELPIE COMING AT YA!)
Name: Kelpie
Personality: To explain what Kelpie's personality is, I'd actually have to explain what a 'kelpie' is. Kelpies are supernatural water creatures/spirits that live in lochs, swamps, rivers, and other bodies of water. They are known to be mischievous and intelligent yet
extremely dangerous creatures that for the most part keep to themselves. They have many unique features and abilities such as: the ability to breath underwater, supernatural strength and speed, shapeshifting/illusion-creating abilities, faint hypnosis skills, and another ability that has yet to be mentioned. Their diet consists of..meat. They prey on other people (or ponies, in this case) by disguising as a beautiful creature, usually a horse or pony, and luring them to the water's edge. As soon as said victim makes physical contact, their Pièce de résistance (the unmentioned skill) comes into play. Their skin becomes extremely adhesive and the victim is stuck. The kelpie then proceeds to drag the victim into the water and eat them.
An important feature of a kelpie is that their mane is always constantly dripping-wet, and with water weeds/flowers in their mane.
Their most important weakness, and the thing that can be the undoing for a kelpie, are bridles. If a kelpie was ever to be bridled, their power would be restrained by the bridle and they would have to submit to the will of whoever bridled them.
TL;DR: Creepy swamp creatures. Think
[This.] Here's the wiki page:
[Link] I'll probably roleplay her personality out as I get the hang of roleplaying again, just to clear up some confusion.
History: Kelpie grew up in the unexplored swamps of Equestria, raised by her family. She was fairly happy (well, as happy as a pony-eating monster can be), but always the slightest bit curious at the outside world. What were the lives of the ponies she preyed on like? What would it be like to be a normal pony, and live in a pony town, and have a Princess, and read and sing and play..
Her family told her to abandon the idea; that the low-lives of their prey weren't worth thinking about. Kelpie followed her parents' advice and eventually "outgrew"' such silly notions. One day, as her family decided to move to another nearby swamp (a single swamp doesn't bring in food forever, you know), a gang of gypsy-ponies ganged upon Kelpie's family and took them by surprise. During the fight and the chaos that followed, Kelpie was separated from her family. Her parents had both managed to be bridled; forever destined to be the slaves of the outsiders. Years passed, and Kelpie learned to fend for her own and moved on to new swamps. She never lost thought of the ideas and dreams she kept tucked away. All she has now are the trinkets and items left behind by the ponies she's killed, tormented by the weight of her unforgivable sins.
Description/Picture: I've got a ref pic of her, but it isn't the way I want it to be, so I'll give you the ref and a short description of her.

Kelpie has light green fur and a dark green mane that is always dripping wet and containing white flowers and water weeds, whether in the water or out. Most of her body (including her legs and wings) are also wrapped with water weed and flowers. Although she has wings and a horn, her wings are more for show and grace than anything else. When she does fly, she usually just 'flits' around from place to place and doesn't fly very fast. Her horn is functional than her wings though, and her magic has a light-green aura.
Cutiemark: Her cutie mark is that of a Swamp Lily.
[Link]Family: She had a family when she was little, but she only vaguely remembers them. She's been alone for most of her life. All that's left are hazy memories and heartache..
Home: A creepy-but-fairly-secluded swamp located near Froggy Bottom Bog.
Likes and Dislikes: Likes: Food. Swamps. Water. Swamp Lilies. Pretty trinkets and shiny things. Music. Poetry/story books (when she can get her hooves on them).
Dislikes: Being disturbed. Being out-of-the-water for extended periods. The thought of being captured.
Other: Some of her most prized "possessions" are an old silver music box that plays
[This] tune, and an
[Old Book] of fairy tales.