A bident is a two-pronged implement resembling a pitchfork. In Greek mythology, the bident is a weapon associated with Hades (Pluto), the ruler of the underworld.
Likewise, the three-pronged trident is the implement of his brother Poseidon (Neptune), god of the seas and earthquakes, while the lightning bolt, which superficially appears to have a single main point or prong, is a symbol of their youngest brother, Zeus (Jupiter), king of the gods and the sky.