I think the third weapon would be Zeus or Jupiter. Zeus was the younger brother of Poseidon (Neptune) and Hades (Pluto). He the god of the sky, thunder and lighting as well as king of the gods.
Also Pluto writin in Latin could be spelled Pluto or Pluton.
Pluto in Greek would be Πλούτων. it's translated to Ploúton. (pronouced as Pluton)