Indra is the king of the Hindu gods and goddesses .The god of strength, foremost in battle. He was the God of thunder, the rainmaker, and the victor over the forces which the Aryans could not vanquish. He symbolizes fortitude and courage. He may be depicted either with two arms or four, and he holds a thunderbolt (vajra) in one hand. He may also carry a bow and arrows, conch shell, a net, or a hook. He has a big belly full of the gods drink called soma. He lives in the city called Indrapura, or heaven. Indra, the god of storms. Indra was once the Vedic king of all gods but has, over time, lost some influence. He became the rain god.

Attributes :

Thunderbolt (Vajra) :
The thunderbolt or diamond that destroys all kinds of ignorance, and it is indestructible. The vajra is symbol of Indra also. In tantric ritual the Vajra symbolised the female principle which represent method in the right hand and the Bell symbolised the female principle, is held in the left. Their interaction leads to enlightenment. Also the Dorje or Vajra represents the “Upaya” or method Tibetans name Vajra as “Dorje”. The thunderbolt or diamond that destroys all kinds of ignorance. The thunderbolt is indestructible and inviolable.

Spear (Skula) :
This is an indestructible weapon

Sword (Khadga):
It is symbols of enlightenment (wisdom), used to destroy ignorance, the enemy of liberation from the bonds of worldly attachments, hence of continuous misery.

Bow and Arrow (Bana and Dhanusha):
Bana is an arrow. It is the symbol of power of love.
The arrow symbolizes the male aspects and the bow the female aspects.
Dhanusa is a bow. It is generally carried in the left hand. It is the symbol of death wish.

(Trap-) cord (pasha):
That which binds or limits the soul and keeps it (for a time) from manifesting its full potential. It symbols the ability of the gods to trap evil and ignorance.

Conch shell (Sankha) :
The conch shell is a music instrument. Its sound chases away demons.
In Hindu tradition, the conch shell seems to have been extensively used in wars by ancient Indian. The white conchs shell whose humming sound proclaims the glory of the saints. It is especially given as a symbol to the gods as the sound vibrated through a shell penetrates far and wide.

Goad (Ankush) :
It symbols the action and the power of discernment regarding to the motives of the mind. It is made of small wooden handle topped by a strong sharp metal hook. The handle is sometimes in the form of Vajra. When the goad is surmounted by a Vajra, it is called Vajrankush.

Riding Animal :

Indra rides a white elephant known as Airavata, the king of the elephants. He may also ride on a golden chariot drawn by 10,000 horses.

Other names of Indra :
Sjachivat (= with power)
Sjachipati (=Lord of Power, later the husband of Sjachi)
Sjakra (powerfull)
Sjatakratoe (=with hundred powers)
Vitra-han (= Vitra-killer).
Sahasraksha (=thousand-eyed)