Koume and Kotake, collectively referred to as Twinrova, are major antagonists in The Legend of Zelda videogame franchise. They serve as the secondary antagonists of Ocarina of Time and the main antagonists of the linked versions of Oracle of Seasons and Oracle of Ages.
The Twinrova are a pair of 400-year-old witches and the surrogate mothers of Ganondorf. Kotake is a master of ice, while Koume is a master of fire. Their fused form is a master of both.
This biography of Twinrova is organized into the latest "official Zelda timeline". This may change completely in the future as the timeline given is merely meant as an example, and there have been official timelines before it.
The Unified Timeline refers to events before the split in Ocarina of Time and thus occurs in every timeline, the split happens in the final battle with Ganon.
Ocarina of Time
They first appear in the 1998 Nintendo 64 game Ocarina of Time, as the boss of the Spirit Temple. They discover Nabooru, a Gerudo warrior, trying to overthrow Ganondorf, and they brainwash her, turning her into a Iron Knuckle. When Link invades the Spirit Temple as an adult, the Twinrova sisters order Nabooru to kill him, but he defeats her and frees her from their grasp. They then make Nabooru disappear once, planning to brainwash her again after dealing with Link.
After wandering onto their sacrificial altar, Link is forced to fight them with his mirror shield. Koume launches beams of fire, which have to be reflected at Kotake, while Kotake shoots beams of ice that must be reflected at Koume. After damaging them enough, they transform into a giant, younger-looking witch called Twinrova, which they call Kotake and Koume's double dynamite attack. To defeat the Witch, Link must absorb three beams of fire or ice into his shield and reflect the attack. After they are defeated, the witches separate and insisted on trying to defeat Link, but Koume notices that Kotake has a halo above her head and Kotake noticed that her sister has one, too. Koume exclaims that she's only 400, but Kotake says she's 380, comedically sparking an argument between the two when Koume yells that they're twins and they can't be older or younger. They continue to squabble until they depart for the afterlife, telling Link that they will come back to haunt him.
This is the timeline where Ganondorf killed Link in his final battle with him, leading to the Imprisoning War described in the backstory of A Link to the Past.
Oracle of Ages/Seasons
Twinrova appears in Oracle of Ages and Oracle of Seasons as the main antagonists, seeking to revive Ganon. After Link defeats Onox and Veran, it is revealed that the villains' real goal was to light two of the three Evil flames needed to revive Ganon. Meanwhile, the sisters kidnapped Zelda in order to steal hope from the people and, in turn, light the Flame of Despair. Since the Evil King needed a vessel, they were also planning to sacrifice Zelda.
Fortunately, Link confronts the witches on time and manages to defeat them. Because of this, they chose to sacrifice their lives, but since they were not the required sacrifice, they only manage to resurrect a mindless, berserker Ganon.
The Twinrova sisters are pretty dangerous here. Koume attacks with fireballs and Kotake with ice balls, which Link must strike to send them back at the other sister. When they fuse, Twinrova can either freeze the ground to slow Link down or create lava pits all over the room. She attacks with fire and ice projectiles that divide into smaller ones. Her weakness in this stage are mystery seeds, but Link must strike her a couple of times with his sword and force her to acquire a neutral and stunned form. Then, Mystery Seeds can be fired at her with either the Seed Shooter or the Hyper Slingshot, which will damage her.
Super Smash Bros.
The Twinrova sisters appear in Super Smash Bros. for 3DS and Super Smash Bros. Ultimate on the Gerudo Valley stage. After the center bridge is destroyed, the witches may show up. They fly around the stage for a while before one of them attacks a side of the stage with an elemental hazard. Koume covers the left side with flames, while Kotake covers the right side with icicle spikes.
In Super Smash Bros. Ultimate, Koume and Kotake also appear as a singular Spirit, being a primary neutral-type. They can be either be summoned using the cores of Charlotte Aulin, Freezie, and Fire Flower, or fought in a Spirit Battle against two Bayonettas, one of which starts with a Fire Flower, while the other starts with a Freezie. At level 99, they can be enhanced to form Twinrova, who boosts the fighter's magical attacks when equipped.