Fairy Legends

In many legends, the fairies are prone to kidnapping humans, either as babies, leaving changelings in their place, or as young men and women. This can be for a time or forever, and may be more or less dangerous to the kidnapped. In the 19th Century Child Ballad, "Lady Isabel and the Elf-Knight", the elf-knight is a Bluebeard figure, and Isabel must trick and kill him to preserve her life. Child Ballad "Tam Lin" reveals that the title character, though living among the fairies and having fairy powers, was in fact an "earthly knight" and, though his life was pleasant now, he feared that the fairies would pay him as their teind (tithe) to hell. Sir Orfeo tells how Sir Orfeo's wife was kidnapped by the King of Faerie and only by trickery and excellent harping ability was he able to win her back. Thomas the Rhymer shows Thomas escaping with less difficulty, but he spends seven years in Faerie. Oisín is harmed not by his stay in Faerie but by his return; when he dismounts, the three centuries that have passed catch up with him, reducing him to an aged man. King Herla also visited Fairy and returned three centuries later; although only some of his men crumbled to dust on dismounting, Herla and his men who did not dismount were trapped on horseback, this being one folkloric account of the origin of the Wild Hunt.

A common feature of the fairies is the use of magic to disguise appearance. Fairy gold is notoriously unreliable, appearing as gold when paid, but soon thereafter revealing itself to be leaves, gorse blossoms, gingerbread cakes, or a variety of other useless things.

These illusions are also implicit in the tales of fairy ointment. Many tales from the British islands tell of a mortal woman summoned to attend a fairy birth — sometimes attending a mortal, kidnapped woman's childbed. Invariably, the woman is given something for the child's eyes, usually an ointment; though mischance, or sometimes curiosity, she uses it on one or both of her own eyes. At that point, she sees where she is; one midwife realizes that she was not attending a great lady in a fine house but her own runaway maid-servant in a wretched cave. She escapes without making her ability known, but sooner or later betrays that she can see the fairies. She is invariably blinded in that eye, or in both if she used the ointment on both.

Source: Wikipedia