In Greek mythology who was punished by Poseidon for boasting about her beauty?

In Greek mythology, the figure punished by Poseidon for boasting about her beauty was the mortal queen Cassiopeia. She claimed that she and her daughter Andromeda were more beautiful than the Nereids, sea nymphs who were beloved by Poseidon. In retaliation, Poseidon sent a sea monster to ravage her kingdom, leading to Andromeda's sacrifice to appease the monster.