The Authority is the name of an angel and one of the primary antagonists of Philip Pullman's trilogy, His Dark Materials.
He was the first angel to come into existence; as did the subsequent angels, he formed and condensed from the substance known as Dust. He led other angels and, later, humanity to believe that he was in fact God, the creator of the multiverse. This false claim legitimized his taking political power in the Kingdom of Heaven. The angel Xaphania later found out the truth about him, whereupon he banished her from the Kingdom (a reference to the legend of Lucifer). Xaphania and some other angels later started a rebellion against him. Several names are ascribed to him, including "Yahweh", "The Lord", "El", "Adonai", and "The Almighty". He is the god of the Christian, Islamic, and Jewish religions and his word and messages to humanity are recorded in the Bible and the Tanakh.
He ruled his various churches, organizations, and universes from the Clouded Mountain, a mobile city believed by many in that universe to be Heaven. As the Authority grew older and weaker, the Mountain became more and more obscured by cloud.
In his old age, the Authority delegated a substantial part of his power to the tyrannical archangel Metatron, who was once the biblical character Enoch, to act as regent of the Kingdom of Heaven. Eventually the traitorous angel grew more powerful than his master, and in greed to usurp the Authority's power and name, trapped him in a crystal box, which keeps him alive but trapped. The two are opposed by Lord Asriel, who allied with "fallen" angels, led by Xaphania in an attempt to overthrow the divine monarchy and replace it with a Republic of Heaven. During the final battle, the Authority is carried away from the Clouded Mountains on the orders of Metatron. The protagonists of the trilogy, Lyra Belacqua and Will Parry free him with the subtle knife, not knowing he is too weak to survive outside the box. He drifts apart and dies in a moment of happiness and peace, presumbly to follow the other deceased characters' precedent by merging with the cosmos.
Philip Pullman, the author of the His Dark Materials trilogy, portrayed the Authority as extremely aged, fragile, kind, and naive, unlike the bitter and thoroughly malicious Metatron. This naivete may probably be one of the reasons of why he believes that he is the original Creator. It may also have made him suseptible to being imprisoned by his traitorous regent Metatron.
The Authority appears only in The Amber Spyglass, the third and final book of the trilogy.