How did pluto end up living in the underworld?

The ancient Roman people were afraid to utter the name of Pluto for fear it would attract the attention of the deity known as the judge of the dead. Pluto was also a god of wealth, as the lord of all the metals and riches that lie under the ground. His name is derived from the Latinized form of the Greek name Plouton, which means wealth.

Pluto was previously referred to as Dis Pater, meaning Father of Gods. However, he is best known for his role as ruler of the underworld and as the counterpart to the Greek god Hades. When the Romans conquered Greece, the gods Hades and Pluto were combined and replaced Dis Pater as the god of wealth, the dead and agriculture.

Origin

The god Pluto lived in a palace in the underworld, far away from the other gods who lived at Mount Olympus. It was his role to claim the souls that inhabited his underworld domain. Those who entered were destined to stay there for eternity. The entrance gates were guarded by his enormous three-headed dog, Cerberus. The three brother gods, Jupiter, Neptune and Pluto, were charged with ruling the worlds after their powerful father Saturn died. Jupiter took the sky, Neptune became ruler of the sea and Pluto's domain was the underworld. Eventually, Jupiter became the supreme god who ruled all of the earth and sky, while Neptune married and stayed in the sea, and Pluto happily remained in the underworld where he presided over the afterlife. Occasionally, he emerged to earth for a visit or a meeting of the gods.

The Abduction of Proserpina

The King of the Gods, Jupiter, had a niece name Proserpina. She was the daughter of his sister Ceres, the goddess in charge of the harvest. In consideration of her valuable domain, everyone, both gods and mortals, did all they could to keep Ceres happy.