The Frog Princess, an old Russian Fairytale (in English):
One Tsar wanted his three sons to marry. He ordered each to shoot an arrow and marry whatever woman lived where the arrow landed. The eldest brother's arrow landed in the courtyard of a boyar's daughter; the middle brother's arrow landed in the yard of a merchant's daughter. The youngest son's arrow went into a swamp. He discovered that a frog had found the arrow and he dutifully but sorrowfully married the frog.
When the tsar ordered his daughters-in-law to make him fine shirts and bake him fine bread, the frog turned into a beautiful princess, Vasilisa the Wise, at night when everyone else was sleeping and made the best shirts and bread.
The Tsar then announced a feast at the palace and commanded his sons to come with their wives. There for the first time Vasilisa the Wise appeared for everyone to see, including her husband Ivan. Later at the dance, Vasilisa performed magical feats with the wave of her sleeves. The wives of the other sons tried to do the same but only succeeded in making a mess.
Prince Ivan, the youngest son, wanted his wife to remain a beautiful princess so he ran home and burned her discarded frog skin. Vasilisa sadly told him that now she would have to become the prisoner of the sorcerer Koshchei the Deathless, and she disappeared.
Searching for her in the forest, Prince Ivan spared several animals who promised to help him in the future. He then came to the hut of a Baba Yaga, a grandmother spirit, who told him he could only free his wife by killing Koshchei. Koshchei's death was well-hidden at the point of a needle, in an egg, in a duck, in a rabbit, in a chest at the top of an oak tree.
Although Ivan could not get the chest out of the tree himself, the animals he had spared broke each thing open until Ivan had the egg. He broke it, broke off the tip of the needle inside, and Koshchei died instantly. Ivan lived happily ever after with Vasilisa.