The Index, in the Halo video game, is an object found on every Halo. It is the figurative key needed to activate the "installation", causing a reaction that will purge the galaxy of sentient life. This removal of all sentient life is to starve the Flood, who cannot be defeated otherwise. It is roughly T-shaped, with a faint blue-green glow emanating from a stripe on each side. Halo cannot be activated unless the Index is inserted into the control panel in Halo's control room.
The Covenant Hierarchs regard the Index as a Sacred Icon.
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