One of the four treasures Black Rabbit had inherited from her Community. This spear has an elemental affinity for lightning. It takes on the appearance of a two pronged golden trident in the anime. Although that this spear (Brahmaastra replica) isn't as strong as the original (Brahmaastra Origin), it is still very powerful.Currently the owner of this spear is Sakamaki Izayoi.
When aimed and thrown at an opponent, it is said to be a Spear of Victory as it will never miss it's target, like an tracker missile. Once it hits its target, the spear will detonate and explode into a blast of light.
In volume 6, when Black Rabbit used the Spear of Indra against His Highness, it has been stated that as long as the Divine Spear which had Fate as an extra Gift hits the target itself, it can override all concepts and defeat the enemy.
In volume 10, after being granted [Divnity] from Indra, Black Rabbit can thrown the Spear of Indra at the Sixth Cosmic Velocity to annihilate Azi Dahaka's clones and an angel
In volume 11, Black Rabbit used the Spear of Indra to pierce through Azi Dahaka's heart at the Sixth Cosmic Velocity. It was stated that the Spear of Indra was also a gift containing Zoroastrianism's cosmology. The Sixth Cosmic Velocity was also stated to be the the speed on the same level with the Star Body.
In volume 12, it has been stated that the spear can move at a speed beyond the speed of light and can crush the whole galaxy.
The Spear of Indra can not display its full strength when used against an opponent who cannot be pierced,as shown when Black Rabbit used it to attack His Highness, not only the spear was unable to pierce through him, but also the mere excess of heat emissions was ineffective too.
Anime: Episode 4
Light Novel: Volume 1, Volume 2, Volume 6, Volume 10, Volume 11
The Spear of Indra shares its name with Indra, the Indian Deity of Thunderstorms and Hindu god called the King of Heaven and the God of Weather and War.