Niobe, a queen of Thebes and wife of Amphion, boasted of her superiority to Leto because she had fourteen children (Niobids), seven sons and seven daughters, while Leto had only two. For her hubris, Apollo killed her sons as they practiced athletics, and Artemis killed her daughters. Apollo and Artemis used poisoned arrows to kill them, though according to some versions a number of the Niobids were spared. Other sources say that Artemis spared one of the girls.(Chloris, usually). Amphion, at the sight of his dead sons, either killed himself or was killed by Zeus after swearing revenge. A devastated Niobe fled to Mount Sipylus in Asia Minor and either turned to stone as she wept or killed herself. Her tears formed the river Achelous. Zeus had turned all the people of Thebes to stone so no one buried the Niobids until the ninth day after their death when the gods themselves entombed them.