Accordingly to some Guaraní myths, Kuarahy (the Sun) and Jasy (the Moon) are brothers, with the Moon being the younger one. As their mother gave birth, the celestial jaguars (a type of evil spirit) killed her and stole the children, raising them in her place. The children eventually grew up and learned the truth, unleashing their vengeance towards the jaguars, killing almost all of them. They spared a pregnant female, who would eventually become the ancestor of all mundane jaguars.

That's the origin of such enmity between man and jaguar - as men took Kuarahy and Jasy's side, and the jaguar their ancestors'. (Jaguars fulfil in Guarani mythology a role similar to the bear in the European ones. It's an animal to fear, to revere, to avoid, to respect, but that you're still bound to fight).

In another myth, that would happen before the brothers' revenge, one of the celestial jaguars (called Charia) was fishing on a river. Charia didn't notice the brothers, so Kuarahy decided to troll Charia a wee bit - diving and pulling Charia's hook and line, to imitate a large fish. Charia pulled the fishing rod with all force, falling behind, amusing the brothers. Kuarahy did this three times, and in all three times Charia fell for it.

Then Jasy, amused, said: "now it's my turn!". He dives and pulls the hook, like his brother did. However this time Charia was quicker - he fished Jasy, killed him with a wooden club, and brought Jasy's corpse home as if it was fish, to eat with his wife.

As they were cooking "the fish", Kuarahy went to Charia's home, and he was invited to partake on the fish. He thanked Charia, but he said that he'd only eat some maize soup; he also asked for the fish bones, allegedly for stock. He took those bones to a remote place, and used his own divinity to resurrect his brother.

That's why lunar eclipses happen - the Moon gets devoured by the evil spirit, with the reddish hue in the sky being the Moon's blood. And the Moon only resurrects, always as a full Moon, because his brother Sun saves and resurrects him.