You will be given a definition of a task first, then some input of the task.
In this task, five ordered key facts are given. All the given facts are expressed in natural language. Your job is to generate a story 100 to 1000 words long, that includes all the facts given as input in their order of appearance while expanding upon them to produce a broader, yet coherent, narrative.

Fact1: Uther 's treacherous younger brother orchestrates coup and sacrifices to become demon knight, Fact2: Uther 's son ends up in Londinium, Fact3: Arthur is caught on ship with hundreds of other men, Fact4: mage identifying Vortigern as acolyte of Merlin presents herself to Uther 's former general, Fact5: Uther 's given vision of how Uther sacrificed himself to save Arthur and entomb sword in stone Darklands
Output:
Mordred, an ironfisted warlock, and his armies lay siege to Camelot, seeking to establish the dominance of magicwielding mages over humankind. Uther Pendragon, king of the Britons, infiltrates Mordreds lair and beheads him, saving Camelot. Uthers treacherous younger brother Vortigern, who covets the throne, orchestrates a coup and sacrifices his wife Elsa to moat hags to become a demon knight, who kills Uthers wife and slays him in combat. The only survivor is Uthers son, who drifts away in a boat and ends up in Londinium, where he is found and raised by prostitutes. Arthur grows into a skilled fighter and man of the streets. Arthur and his friends confront a group of Vikings who had mistreated one of the prostitutes, forcing him to pay her restitution. Afterwards, the brothel is raided by the Blacklegs, Vortigerns minions, and Arthur learns that the Vikings were under the kings protection. Arthur tries to escape the city but is caught and put on a ship with hundreds of other men; the Blacklegs have been forcing all men of Arthurs age to try to pull a sword that has appeared near the castle from the surrounding stone. Arthur is able to remove the sword but is quickly overwhelmed by its power and passes out. Vortigern meets with him in the dungeon, revealing his true lineage. Meanwhile, a mage identifying herself as an acolyte of Merlin presents herself to Uthers former general, Sir Bedivere. At Arthurs planned execution, the mage uses her magic to stage a diversion while Bediveres men rescue Arthur. Taken to Bediveres hideout, Arthur initially refuses to help them. The mage persuades Bedivere to take Arthur to a realm called the Darklands, where hes given a vision of how Uther sacrificed himself to save Arthur and entomb the sword in stone. Arthur learns Vortigern was responsible for persuading Mordred to rebel against humanity, and he returns determined to destroy Vortigern. With his friends and Bediveres men, Arthur stages a series of ambushes against Vortigern, culminating in an assassination attempt in Londinium. The rebels sense a trap but attack anyway, fleeing to a fighters school run by Arthurs mentor George, where they are overrun by the Blacklegs. Seeing the mage held at knifepoint, Arthur unleashes Excaliburs potential, singlehandedly killing all of the soldiers. The rebels are able to escape the city except for Arthurs injured friend Back Lack, who is killed at Vortigerns hand in front of his son Blue. Ashamed of his failures, Arthur tries to throw away the sword, but the Lady of the Lake returns it and shows him a vision of Englands future under Vortigerns rule. Coming to terms with his responsibility, Arthur reunites with Bedivere. When they return to the rebel hideout, however, they discover all of their allies dead, Vortigern having found them and delivered an ultimatum: if Arthur does not surrender himself, the captured mage and Blue will die. Arthur surrenders himself, but as Vortigern is about to execute his nephew, a giant snake summoned by the mage attacks and devours Vortigerns men. While Bedivere and the others lead an attack on the castle, a desperate Vortigern sacrifices his only daughter and is transformed into the demon knight, confronting Arthur in a separate dimension. Despite his fighting skill, Arthur is beaten, and he is about to submit when he witnesses a vision of his father, convincing him to accept the sword and his character as his own. Arthur violently slays Vortigern but blesses him as he dies. In the aftermath, Arthur dissolves Vortigerns pact with the Vikings and begins building a Round Table where his knighted friends will meet. Blue and the prostitutes arrive with the crown of Uther, which Arthur accepts, holding the sword aloft.