Final Judgment

Final Judgment is an event that is derived in Abrahamic religions, and is described in the New Testament of the Holy Bible, where God performs his final and eternal judgment upon every nation.

Background
Although apparent in every Abrahamic religion, it is most notable in Christianity as it is thoroughly recorded in the Bible, most prominently in the New Testament, especially the, though it is hinted at in the Old Testament as well.

In the Toaru Majutsu no Index universe, because of God's plans for humanity to be judged at the end of the world, where he will descend in to mortal world, and whither He shall decide the fate of all of humanity. Hither, He shall judge everyone; the good will be partitioned for Heaven and the wicked will be partitioned into Hell. Angels are not allowed to save or kill anyone as it may change history, as God already has knowledge of those to be judged at the Final Judgment beforehand. Kanzaki Kaori explains further that if angels did that history would be changed, and may create a paradox in spacetime. For example; a person who should not be killed is killed by an angel, their children will not be born, and so on and so forth, this presumes that their descendants may be part of the Final Judgment of God at the end of times.

Angel Fall Arc
The Final Judgment is briefly referenced by Tsuchimikado Motoharu and Kanzaki Kaori to Kamijou Touma as one of the reasons they should stop Angel Fall as soon as possible, as it has caused an angel to fall down to Earth.