Twinrova

Twinrova are a pair of witches that feature in several Zelda games, most notably in Ocarina of Time, in which they act as the boss of the Spirit Temple. The two sisters, Koume - sorceress of flame, and Kotake - sorceress of Ice, are able to fight individually with elemental attacks or combine together into a more powerful form.

Ocarina of Time
The first appearance of Twinrova had them abducting Nabooru in the Spirit Temple. As an adult, Link faces them after reaching the boss room of the temple, and defeats them by reflecting the elemental attacks of one sister at the other using the Mirror Shield.

If Navi is consulted during the battle with Twinrova in her ultimate form, she will react with great fear, indicating that Twinrova is a legendary terror.

Majora's Mask
In the Southern Swamp, Koume and Kotake operate the Swamp Boat Tour and the Magic Hags' Potion Shop. While searching for mushrooms in the Woods of Mystery, Koume was attacked by the Skull Kid and rendered immobile until Link revived her with a Red Potion from Kotake.

Oracle of Ages and Oracle of Seasons
Twinrova appeared as the second-to-last boss in the linked Oracle games.

Trivia

 * Twinrova served as a surrogate mother to Ganondorf in Ocarina of Time.
 * "Koume" is a Japanese pickled plum.
 * "Kotake" is a type of Japanese mushroom.