In Roman mythology, the god of the underworld is Pluto, also known as Dis Pater. He presides over the realm of the dead and oversees the souls that enter his domain. Pluto is often depicted not as a malevolent figure but as one who ensures the natural cycle of life and death. He plays a crucial role in the mythological narrative, interacting with both gods and mortals and representing the inevitability of fate and the afterlife.