Agni's Festival Fire

Agni's Festival Fire (アグニの祭火) is a magic spell that is used by the magic cabal Gate of the Gods Descended from Heaven. As its name suggests, it is a large-scale magic spell. Based originally from the Agni Astra, it can be modified to create a highly destructive large-scale magic spell. It's infamous as the spell being used to attack a large sports gym in New Delhi two years prior to the main storyline of Toaru Majutsu no Index.

It's usage by the magic cabal is what throws Kamijou Touma into the plot of Toaru Majutsu no Index: Road to Endymion.

Base
Agni is a Hindu god associated with fire and lightning, as such, the magic cabal uses these attributes for the spell. This is in contrast with its base form the Agni Astra, which uses the fact that Agni held the attribute of light to send out a code in the form of lights that blink at a regular interval, a form of communication based on the length of the flashes.

Setup
To use the spell requires the alteration of the output of electromagnetic waves, which in turn can cause a large scale disaster. In the magic cabal's case, when using for the operation against Academy City, they had set-up the magic circles for the spell on the wind turbines using a powerful ultraviolet light in order for the paint to slightly fade. This was used to make the magic circle harder to see. Each magic circle makes up a part of the whole spell. Despite the large number of magic circles used by the magic cabal for their operation in Academy City, the number of its users are limited. It requires the magic circles to be connected to a terminal, which in turn, connects to the single central point, which controls the spell. Using the symbolism of Shiva, the Hindu god and ruler over everything that flows, who has a strong connection with Rudra, the Hindu god of roaring wind, the magic cabal allows for the center to send out commands to the terminals.

If needed, like when the center is destroyed, the magic cabal is apparently either able to switch to a backup center or have a spiritual item that makes of an existing terminal into the new center.

Activation
The spell appears as a bluish-white linging with the sound of fireworks going off, immediately after, flames explode on the area, although this is just a small-scale version of the spell.

The spell is used for a specific targets, the magician Sozty Exica uses a smaller scale version of Agni's Fire Festival, she interferes with the terminals set up on the turbines to acquire attack power at an individual level. She uses the fact that Agni's Festival Fire use a Shiva-based communications method as a means to acquire targeting information. However, this method of targeting is inaccurate depending on the area where she uses the spell. The flow of the wind surrounding the complex array of buildings of Academy City causes intereferences with the targeting method, while a single straight tunnel does not. The spell apparently also requires a chant of some sort before activation.