Mukunga M'bura, the mythic rainbow, is a predatory monster who lives in water. The rainbow in the water and the sky is not the animal himself but his reflection. When he comes out at night, his tail remains in the water. When the rain comes, the rainbow puts his head out of the water and lies on his back and turns red and is reflected in the sky; at other times, he is green. He eats goats and cattle.
The rainbow that lived in the Lake of Naivasha came out of the water at night and stole the cattle of the Masai, who lived in a village not far from its borders. When he had done this, not only once but twice, the young warriors prepared a reception for him—they made their spears hot in the fire and awaited his coming. The only vulnerable part of a rainbow is the back of his neck. When therefore the monster once more made a descent on the cattle, the young men carefully judged their aim and plunged their spears into his neck behind his head, and the rainbow, wounded, fell dead.
In a myth, a boy herds cattle on the grazing grounds of Mukunga M'bura, who, in retaliation, swallows the boy's father and all the people, the livestock, and the homes, all except the boy. As the boy grows to manhood, he takes a sword and goes to fight Mukunga M'bura, who, fearing the youth, implores him to make a hole in his finger rather than his heart, so that he will survive. The youth does so, and everything Mukunga M'bura has swallowed emerges. The youth initially spares Mukunga M'bura, but later, fearing his evil, he goes back and kills him. But one leg of Mukunga M'bura throws itself into a pool. When, the following day, the youth goes to destroy the leg, he finds no water, only the livestock that had remained in Mukunga M'bura.