Before the arrival of the Spaniards, the lands around Iguazu Falls belonged to the Guarani Indians. Every year, the Guarani tribe sacrificed a young virgin to M'Boi, the serpent god who lived in the river. One day, a girl called Naipi was walking near the river and M’Boi saw her reflection in the water. The Serpent God thought she was the most beautiful woman he had ever seen and demanded that the Guarani tribe give her to him. The elders of the tribe were too afraid to upset M’Boi because his father was Tupa, the Supreme God of All, so they made arrangements to sacrifice Naipi a day before her marriage with Taruba, a great warrior from a neighboring tribe. Naipi was devastated, as she and Taruba were madly in love. Taruba was furious and believed he could rescue Naipi from her grim fate. The lovers made arrangements to meet at the Iguazu River and runaway. Unfortunately M’Boi saw them climbing into the canoe and raced to catch up with them.
Taruba rowed as hard as he could and was able to keep a few feet of space between them and the serpent. This made M’Boi so mad that his body expanded to the size of the river. He slithered and squirmed causing the river to form new curves and the little canoe to rock back and forth. When Taruba wouldn’t give up, M’Boi became absolutely furious, and he forced the earth to split. The river spilled over the cracked earth, sending the canoe into downfall. Taruba was knocked out and tossed onto the embankment. Naipi was trapped inside and about to be smashed into the ground below when M’Boi transformed her into a large rock, so she wouldn’t be able to run away. Taruba tried to rush down to her, but his hands were pulled into the earth by M’Boi. His fingers were stretched so deep into the embankment that they turned into roots and Taruba grew into a palm tree - forever rooted to the earth above the falls.
This was M’Boi’s way of revenge, separating the two lovers by an enormous waterfall, so they could see each other but never touch. M’Boi is said to lurk deep in the water’s of Devil’s Throat, watching the palm tree and the rock, making sure that they never unite. Although Naipi and Taruba can never be together, they still manage to show their love by forming a rainbow which starts at a palm tree on the Brazilian side of the falls and reaches over to the rock of Naipi in Argentina.