Twinrova

Kotake and Koume, collectively known as Twinrova, are a pair of Gerudo witches who 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 known as Twinrova. They are both the surrogate mothers of the Gerudo King, Ganondorf, being among his more devoted servants.

Their specialty is brainwashing others to serve Ganondorf (most notably Nabooru) and merging to form the stronger witch "Twinrova," where their combined power is much deadlier. The brooms the sisters use to fly become scepters with which Twinrova performs her spells.

Ocarina of Time
Kotake is the Gerudo Sorceress of Ice and claims her magic will "Freeze [Link] to his soul." Her twin sister is Koume and she is one of Ganondorf's surrogate mothers. Like Koume she has green, wrinkled skin and dresses in black robes with white Gerudo pattern near the hems and an obi-like belt around her waist. In correlation with her element, ice, she has a blue jewel on her forehead, blue slippers, and the markings on her headband are in red with a blue border. Her only weakness is her sister's flames.

Majora's Mask
In Majora's Mask, Kotake is the owner of the Magic Hags' Potion Shop, where she sells the standard selection of Red Potion, Green Potion, and Blue Potion. However, she doesn't sell Blue Potions right away - she requires a Magic Mushroom, which she will happily take from Link if offered to her, and she will use it to create the Blue Potion which will be available for the remainder of the three days.

Kotake cares for her sister quite a bit. When Kotake hears that Koume was attacked by Skull Kid in the Woods of Mystery, she gives Link a bottle of Red Potion to deliver to Koume. If a whole day passes and Link does nothing to help, Kotake will leave her shop and proceed to the Woods of Mystery herself to search for Koume.

Ocarina of Time
Koume is the Gerudo Sorceress of Flame and claims her magic will "Burn [Link] to his bones." Her twin sister is Kotake and she is one of Ganondorf's surrogate mothers. Like Kotake, she has greenish tinged, wrinkled skin and dresses in black robes with white Gerudo pattern near the hems and an obi-like belt around her waist. In correlation with her element, fire, she has a red jewel on her forehead, red slippers, and the markings on her headband are in blue with a red border. Her only weakness is her sister's ice.

Koume tends to adopt the role of leader of the two, usually appearing first and deciding their course of action (she was the first to introduce herself during the boss battle and also came up with the idea to combine with Kotake to form Twinrova).

Majora's Mask
In Majora's Mask, Koume is the guide for Swamp Boat Tour. She occasionally goes into the Woods of Mystery to look for mushrooms for Kotake to use in the Magic Hags' Potion Shop. However, one day she ran into the Skull Kid and was injured. Link is sent by her sister to find her in the nearby woods. Upon discovering her, she asks for Red Potion to heal her. If Link tries to give her a potion in any form other than his human one, she calls him a "Weirdo" and tries to avoid his attention by playing dead. Once Link gives her the potion, she returns to her post at the Swamp Boat Tour, where she gives Link one free tour in return for healing her.

Twinrova
During Link's final confrontation with them in the Spirit Temple, Koume and Kotake fight using magic bolts of the elements from which their power comes: fire and ice. Using the Mirror Shield, Link is able to redirect the attacks of one sister against the other. After taking a total of four hits, the pair will use their "Double Dynamite Attack" and merge into Twinrova, a single being with the combined powers of both witches. Before the battle starts, Link flinches in shock and Twinrova winks at him.

Once merged into Twinrova, the Mirror Shield remains essential in winning the battle. Link is able to use it to absorb the power of both the fire and ice spells. He is required to collect three consecutive charges of one type of spell, which then allows him to release the spell back at Twinrova. However, since Twinrova frequently alternates between fire and ice attacks, care must be taken to only block attacks of one type at a time; blocking a fire attack followed by an ice attack, or vice versa, will cause all power currently stored in the Mirror Shield to dissipate.

Once Twinrova is injured by the reflected attack, she collapses on one of the four outlying platforms, allowing Link the opportunity attack with his sword. After a sufficient number of strikes Twinrova will be defeated, at which point she will split back into Koume and Kotake. The two witches then say they are going to get "get serious," but realize shortly thereafter that they have halos above their heads. The witches' distress over their defeat fades when their conversations turns into an argument about their age, after which they ascend to the afterlife in a column of bright light.

Trivia

 * Twinrova served as a surrogate mother to Ganondorf in Ocarina of Time.
 * It can be assumed that in Majora's Mask, Kotake supplies Clock Town with potions due to the fact that if Link gives Koume a red potion purchased at the Trading post she still states that it smells like one of Kotake's.
 * On an interesting note, the Hylian writing on Kotake's and Koume's headbands is in fact the different, new Hylian alphabet used in The Wind Waker, and not the one used everywhere else in Ocarina of Time. The bands simply say "Kotake" and "Koume".
 * "Koume" is a Japanese pickled plum.
 * "Kotake" is a type of Japanese mushroom.
 * Kotake and Koume are called "Killa Ohmaz" (Killa Grannyz) and Twinrova is called "Sexy Thermo Hexy" (Sexy Thermo Witchy) in the German Version of Ocarina of Time.
 * The scene where the Twinrova sisters brainwash Nabooru again is included in the introductory cutscenes of the game (seen when the player doesn't press Start yet).