In Western mythology the trident was the attribute of the Greek
god Poseidon, the aquatic god of the seas, storms and
earthquakes, who later became the Roman maritime god, Neptune.
The watery planet Neptune is represented astrologically by the
trident, which as a fish-spear formed the most versatile
implement for spearing fish. In early Christian art the trident
formed a symbol for the trinity of Father, Son, and Holy Ghost,
but later the trident was identified with Satan or Lucifer, and
his trident became the pitchfork of the denizens of hell.
The symbol of the trident - meaning 'three teeth' - first
appeared on Mesopotamian clay seals, and on early Shaivite seals
unearthed from the ancient Harappan civilization of the Indus
valley. In Vedic mythology the three point of the trishula -
meaning 'three iron spikes or stakes' - are identified with the
three prongs of Indra's vajra or 'thunderbolt', and early
representations of Indra's vajra often depict it as a
double-ended trident. The three points symbolize the Hindu
trinity of Brahma, Vishnu and Shiva, and the three vibration
sounds - AUM - of the sacred syllable Om. As the main emblem of
Shiva, the trishula's three point represent his transcendence
over the three gunas or qualities of nature: rajas - the dynamic
or passionate quality of Brahma as creator; sattva - the wisdom
or pure quality of Vishnu as preserver; and tamas - the inert of
dark quality of Shiva as destroyer. Shiva's trident also
symbolizes his control over the three realms of heaven, earth and
underworld; his triumph over the three times of past, present,
and future; and his form as the 'Lord of the Three Rivers' or
triple braid' (Skt. triveni). Triveni refers to the sacred site
of Prayaga (modern Allahabad), where two rivers of the Ganges and
Yamuna unite with the hidden underground river of Saraswati.
Esoterically this symbolizes the 'third eye' point between the
eyebrows, where the lunar and solar channels unite with the
central channel. The shaft of the trishula represents the central
channel of sushumna, by which the goddess Kundalini ascends to
unite with her lord, Shiva, in the 'thousand-petalled lotus'
(sahasrara chakra padma). As the median nerve, or as the axis of
Mt Meru, which rises from the earth into the heavens, the shaft
serves as a conduit between the devotees of Shiva and their lord.
The iron trishula is found in every Shaivite shrine scattered
throughout India, and is often adorned with the bangles of female
devotees as a supplication for fertility, the birth of a son, or
as a symbol of betrothal to Lord Shiva.