Changeling

A Changling a person that has a fairy implanted in them from birth. This happends to Princess Elena whom after her birth and the death of her mother during childbirth, was visted by a Sidhe elder that started a 20 year plot that cast a spell on her. He then had his Pixie servant, Grunhilda disguise herself as a Human and become her nurse. Grunhilda regularly sprinkled her with dust as she slept so that when the time was right, the Sidhe inside her would completely possess her. The right time being when she married Arthur Pendragon.

Known Changeling
Only Princess Elena is the known one.

Folklore
A changeling is a creature found in Western European folklore and folk religion.. It is typically described as being the offspring of a fairy (Sidhe), troll, elf or any other legendary creature that has been secretly left in the place of a human child. The theme of the swapped child is common among medieval literature and reflects concern over infants afflicted by as-then unknown diseases, disorders, or mental retardation.

A human child might be taken due to many factors: to act as a servant, the love of a human child, or malice. Most often it was thought that fairies exchanged the children. Some Norwegian tales tell that the change was made to prevent inbreeding: to give trolls and humans new blood, humans were given children with enormous strength as a reward. In some rare cases, the very elderly of the Fairy people would be exchanged in the place of a human babe, and then the old fairy could live in comfort, being coddled by its human parents. Simple charms, such as an inverted coat or open iron scissors left where the child sleeps, were thought to ward them off; other measures included a constant watch over the child.

In Scottish folklore, the children might be replacements for fairy children in the tithe to Hell. Also, according to common Scottish myths, a child born with a caul (head helmet) across their face is a changeling, and of fey birth.

Some folklorists believe that fairies were memories of inhabitants of various regions in Europe who had been driven into hiding by invaders. They held that changelings had actually occurred; the hiding people would exchange their own sickly children for the healthy children of the invaders.

In other folklore, the changelings are put in place of the child to feed off of the mother of the child. The kidnapped child then becomes food for the changeling's mother. This is done for the survival of their kind. Once the changeling mother and the changeling have drained the life from the human mother and child, the changeling and its mother begin to search for a new suitable food source. Other sources[2] say that human milk is necessary for fairy children to survive. In these cases either the newborn human child would be switched with a fairy babe to be suckled by the human mother, or the human mother would be taken back to the fairy world to breastfeed the fairy babies. It is also thought that human midwives were necessary to bring fairy babes into the world.

Some people believed that trolls would take unbaptized children. Once children had been baptized and therefore become part of the Church, the trolls could not take them. One belief is that trolls thought that being raised by humans was something very classy, and that they therefore wanted to give their own children a human upbringing.

Beauty in human children and young women, particularly blond hair, attracted the fairies.

Some changelings might forget they are not human and proceed to live a human life. Changelings which do not forget, however, may later return to their fairy family, possibly leaving the human family without warning. As for the human child that was taken, he or she may often stay with the fairy family forever.

Facts in History
Two 19th century cases reflected the belief in changelings. In 1826, Anne Roche bathed Michael Leahy, a four-year-old boy unable to speak or stand, three times in the Flesk; he drowned the third time. She swore that she was merely attempting to drive the fairy out of him, and the jury acquitted her of murder. In the 1890s in Ireland, Bridget Cleary was killed by several people, including her husband and cousins, after a short bout of illness (probably pneumonia). Local storyteller Jack Dunne accused Bridget of being a fairy changeling. It is debatable whether her husband, Michael, actually believed her to be a fairy – many believe he concocted a "fairy defence" after he murdered his wife in a fit of rage. The killers were convicted of manslaughter rather than murder, as even after the death they claimed that they were convinced they had killed a changeling, not Bridget Cleary.