Vasavi Shakti

"Know the mercy of the King of the Gods. Indra, watch over me with keen interest! With this single strike, I shall inflict extinction. Be reduced to cinders, Vasavi Shakti!"

- Karna

Vasavi Shakti: O Sun, Abide to Death is a spear of light that can even kill gods. It is a spear of mortality made out of lightning that is manifested by converting his golden armor, Kavacha and Kundala, due to Indra snatching it away in the legend and then rewarding Karna's noble posture with the spear. It can only be used once, exchanging tremendous defensive power to equip a spear with a powerful "anti-god" performance. A spear of light that even the king of gods was not able to handle properly, the single strike released by peeling off his whole body and being dyed in blood purges all sorts of impurities.

The spear transforms and officially becomes this Noble Phantasm after he sheds his golden armor, but it's not like the spear he usually uses is a fake, but it can’t activate its name of “Vasavi Shakti: O Sun, Abide to Death” in that state. It is a massive spear, far longer than the man himself is tall. The spear of light is so enormous that it does not seem possible for a human to wield, and of such exquisite appearance that it is practically a work of art. It can only be described as a weapon granted by the Gods that was said to be capable of even killing gods.

The secret weapons among secret weapons, which doesn’t exist even in the treasure vault of the King of Heroes. Gilgamesh calls it a spear that cannot be used by anyone and "an article of rare beauty none have ever laid eyes upon." Due to Karna having obtained it in the legend and having never used it, it is impossible to tell if there is a corresponding treasure in the Gate of Babylon.

Although Karna gives his armor to Jinako Carigiri in Fate/Extra CCC, he still manages to partially utilize the ability without what actually forms it, but he is left close to death after his battle with Hakuno Kishinami's Servant due to that. When utilized, he lifts into the air, causing the wing-like armor on his back to spread out into a wing of flame and manifests an identical wing and armor opposite of it. Pointing his spear at the enemy, the flames gather in the ring between the wings and converge into the spear. Released upon the enemy as a beam of light from the tip of the spear, it engulfs them in a massive explosion. The armor shatters into a number of red feathers that quickly fade away, causing him to say "it was inevitable", while reducing his defense and causing his attack to be raised as he continues to battle.

Development
pako is the weapon designer for Vasavi Shakti. Kinoko Nasu calls it an Indian version of a Buster Launcher that projects a giant lightning beam.