Trisula becomes the 'sceptre of diamonds' of Indra the storm god. The vajra or thunderbolt has been likened to the discus of Vishnu and like the celestial two headed mallet or double hammer of Thor, is a weapon of the gods typifying lightning, rain and thus life and fertility.
The Chaldeans figured a thunderbolt by a trident. In Nimroud it is held in the left hand of a god who holds an axe in the right. As the axe is a sun symbol and the trident is given to gods of storm and water we have here again the powerful union of fire and water. The Vajra appears in Mesopotamia as a double trident. Marduk in fighting with the monster Tiamat is depicted with a double trident in each hand. A trisula or trident with zigzag shaped points to typify lightning is frequently shown in the hands of Assyrian gods.
The Trident is the symbol of Poseidon (Neptune) the god of water, and the suggestion has been made that it typifies the third place the sea holds after heaven and air.
In Egypt the Trident or Trisula is associated with the winged sun disk.