Poseidon's infatuation with Demeter led to the creation of the horse. He built the impenetrable walls of Troy with the god Apollo. Poseidon unintentionally fathered many heroes, including Theseus, and many creatures, such as the Polyphemus and the Pegasus. Poseidon's accomplishments are usually results of his volatile moods and uncontrolled urges, such as his seduction of Medusa in Athena's temple, which caused Medusa to transform into a gorgon.
In the horse creation myth, Poseidon pursued Demeter, the goddess of agriculture and growth, but she would not have him. Finally, she warmed up to him and requested that he make her something exceedingly beautiful. Poseidon acquiesced and spent ages shaping and molding beautiful creatures until he created the horse. By the time his work was finished, his desire subsided.
Greek mythology also credits Poseidon with the Walls of Troy. Poseidon and Zeus often quarrelled, which led to an alliance between Apollo and Poseidon to overthrow him. Zeus uncovered their plan. As punishment, Poseidon and Apollo were made to work for mortal wages for Laomedon, the fifth King of Troy. Poseidon is the god of all things that rumble from beneath, including earthquakes, landslides and horses, which were said to create a terrifying noise when galloping into battle. Like the sea, his domain, he has a volatile personality and temper.