Auriel's Bow is an artifact used by the elven god Auriel, an aspect of the Imperial Akatosh, the Dragon God of Time. Although it takes the form of a modest elven moonstone bow, it is one of the most powerful weapons on Tamriel.
The bow draws its power from Aetherius itself, channeling it through the sun. It has the ability to turn any arrow into a "missile of death", although its enchantment effects vary: it has been known to cause magical fire or shock damage, drain an opponent's stamina and magicka reserves, or harness the power of the sun. It can also make the wielder immune to lesser attacks, and is especially devastating when used against the undead. Occasionally it can be seemingly unenchanted. Without Auriel's power behind it, however, the bow uses its own store of energy for its power. Once exhausted of this energy, the bow will vanish, abandoning its owner to reappear elsewhere.
Because of its link to Auriel, the bow can manipulate the sun in various ways. It was involved in a prophecy recorded in the Elder Scrolls, which foretold that the bow would be used to block out the sun. The bow is twinned with Auriel's Shield and presumably Auriel's Quiver. It purportedly smells like ash yams, a vegetable native to Morrowind.
Legend says that in the Dawn Era, the bow was created by Anuiel for use by Auriel against the forces of Lorkhan during the Ehlnofey wars. When Trinimac defeated Lorkhan and tore out his heart, Auriel fastened it to an arrow and shot it long into the sea, where Red Mountain eventually formed.
The bow was traditionally held by the Chantry of Auri-El, the epicenter of the Snow Elf religion which was based in the secluded Forgotten Vale of Skyrim. The Snow Elves had discovered how to use the bow's ability to harness the power of the sun to greater effect, through the use of Sunhallowed Elven Arrows. These arrows could be fired at an enemy for massive sun damage, or could be fired directly at the sun to use its rays to strike down all foes in the surrounding area. Due to its isolation, the inhabitants of the Chantry avoided being enslaved by the Dwemer or killed by the Nords.
The bow's involvement with the Tyranny of the Sun prophecy began when Vyrthur, the Arch-Curate of Auriel, was infected with vampirism by one of his own initiates. Despite Vyrthur's devotion to Auriel, the god turned his back on him when he became undead. He swore revenge against Auriel; unable to kill a god, Vyrthur instead sought to destroy his influence on Nirn by blocking the sun. To achieve this, he needed to corrupt the bow itself with the blood of a Daughter of Coldharbour, i.e. a pure-blooded female Vampire Lord who had received the disease directly from its creator, Molag Bal. Vyrthur allied himself with the Betrayed, the degenerated Falmer who had been crippled by the Dwemer and by centuries of living underground, and killed most members of the Chantry, claiming control of Auriel's Chapel to lay in wait for the prophecy to come true.
For hundreds of years, the bow appeared throughout Tamriel, with its most recent appearances being the subject of gossip. The bow was uncovered by the Eternal Champion during the Imperial Simulacrum, in the province of Valenwood, Skyrim or Elsweyr (accounts vary). In the events leading up to the Warp in the West, a clue to the bow's location was discovered by a witch living in the Iliac Bay region. In return for kidnapping the witch's great-granddaughter to become the witch's successor, she revealed the clue to a questing member of a knightly order, who retrieved it from the dungeon where it lay. A fake copy of the bow also appeared in the Iliac Bay around this time; it was created by a mage in an attempt to bribe an agent of Nocturnal who has been sent to assassinate him. The fake bow functioned identically to the true artifact, but after several days it crumbled to dust.
Later in the Third Era, the bow was claimed by Ralyn Othravel, a Dunmer Ordinator and member of the Tribunal Temple stationed at Ghostgate, a small military settlement along the Great Ghost Fence on Vvardenfell. In 3E 427, Mistress Therana, an eccentric Councilor of Great House Telvanni, discovered the bow's location through unknown means, although she claimed she could smell its ash yam scent. A member of House Telvanni took the bow from Ralyn Othravel and gave it to Therana, who grudgingly accepted it. Later that year, the bow was sold to Torasa Aram, who put it on display in her Museum of Artifacts in Mournhold.
In 4E 201, the Tyranny of the Sun prophecy was realized with the awakening of Serana, an ancient Daughter of Coldharbour, by the reformed Dawnguard. Serana was the daughter of Lord Harkon, the leader of the Volkihar vampire clan, who had spent centuries attempting to fulfill the prophecy. The prophecy brought Serana and the Last Dragonborn to the Forgotten Vale, where they encountered Knight-Paladin Gelebor, the lone survivor of his brother Vyrthur's attacks on the Chantry of Auriel. The two ventured into the ruins of the Snow Elf chapel and defeated Vyrthur, who had planned to use Serana's blood to fulfill the prophecy. Auriel's Bow was retrieved and subsequently used to slay Lord Harkon.