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It is hubris - the excessive pride which offends gods. In Book 9, Odysseus just can't resist from revealing his true identity to Cyclops, even though he is aware how dangerous it is. He will suffer from Poseidon's anger because of it. In Book 12, he tries to fight Skylla instead of just sacrificing a few warriors, as Circe had recommended him. Soon enough, he realizes that he couldn't possibly defeat the monster, so he lets her devour six of his friends, and barely escapes alive, with the rest of his people.