The Elder Scrolls V: Skyrim - Dawnguard
Tags: good versus evil

Plot synopsis:
The player character may begin the expansion quest lines in a number of ways. Town guards can be overheard discussing the return of the Dawnguard, or the player character may be approached directly by an Orcish Dawnguard member named Durak and asked to join the order to combat the growing threat of vampires within Skyrim. Regardless of how it is initiated, the player character travels to Fort Dawnguard, accessible through Dayspring Canyon, located near Riften. They meet with the Dawnguard commander, Isran, who reiterates the renewed strength and threat of the vampires, citing their destruction of the headquarters of the Vigilants of Stendarr as reason to reform the Dawnguard and eradicate the vampires. The player character is given a crossbow and asked to travel to a ruin the vampires are known to be investigating. Upon arrival, the player discovers a vampire named Serana (voiced by Laura Bailey) trapped inside a statue. She is in possession of an Elder Scroll, and informs the player that her family live in a dwelling off the coast of Skyrim, near Solitude, called Castle Volkihar. She asks the player character to escort her safely back to her home. When she has been returned home, her father, the vampire Lord Harkon, offers the player the chance to become a vampire lord out of apparent gratitude for his daughter's safety, or the chance to leave Castle Volkihar safely and return to the Dawnguard. This choice begins the main storyline of Dawnguard.
=== Volkihar path ===
If the player accepts Lord Harkon's offer, the vampire lord bites the player character. The player awakens in a room, in front of a shrine to the Daedric prince, Molag Bal. Harkon explains Molag Bal is considered the "father of [his] kind". Thousands of years ago, Harkon was a king and a mortal. He pledged his soul to Molag Bal, and sacrificed "a thousand innocents" in his name. The Daedra granted Harkon and his family immortality by afflicting them with vampirism. Harkon shows the player character how to utilize their new vampire lord form and powers. The player is then tasked with retrieving the Bloodstone Chalice, a powerful artifact intended to aid Harkon's cause, to fill it with water from Redwater Den, and then to add the blood of a powerful vampire. While retrieving the Chalice, the player character is attacked by two of the Volkihar, Stalf and Salonia, who are plotting to overthrow Harkon. After killing them, the player adds their blood to the Chalice and returns to Castle Volkihar.
After receiving the Chalice, Harkon spreads false rumors around Skyrim regarding the alleged discovery of an Elder Scroll, to try and lure a Moth Priest to the land. The Moth Priests are an ancient order, capable of looking upon the Elder Scrolls and deciphering prophecy from them. The player travels to Forebear's Hideout, and captures a Moth Priest named Dexion Evicus. The player turns the Priest into a thrall, and upon reading the Scroll, Evicus reveals to the Volkihar that they need to locate a weapon named Auriel's Bow, as well as two more Elder Scrolls. One of the Scrolls lies within the Dwemer ruin of Blackreach, and is retrieved as part of the original main quest line. The other was taken by Serana's estranged mother, Valerica, when she fled the castle. The player character and Serana journey to a plane of Oblivion known as the Soul Cairn. They locate Valerica and retrieve the final Elder Scroll. Before they return to Tamriel, Valerica warns them to stop Harkon, as he intends to kill Serana to fulfill the prophecy.
The player character learns from the Elder Scrolls that Auriel's Bow is located in Darkfall Cave. The player meets with Gelebor, one of the last remaining Snow Elves, and a Knight-Paladin of the Chantry of Auri-El. He instructs the player how to retrieve Auriel's Bow, by completing a series of tasks and defeating Arch-Curate Vyrthur, Gelebor's brother, who has been corrupted by the Falmer. The player character and Serana confront Vyrthur and discover that he is both a vampire and the creator of the prophecy, and desires to block out of the sun in order to disrupt Auri-El's influence in Tamriel, in retaliation for the god allowing him to be afflicted with vampirism.
After retrieving the Bow, the player character and Serana confront Lord Harkon in Castle Volkihar. They battle Harkon and slay him, ending the threat to Tamriel and to Serana, and the members of Harkon's court acknowledge the player character as their new master.
=== Dawnguard path ===
If the player character refuses Harkon's offer and returns to the Dawnguard, the plot plays out nearly identically, albeit viewed from the perspective of the Dawnguard. Serana makes herself known to the Dawnguard, relaying information about Harkon's plan, and pledging assistance to the Dawnguard. In order to enter the Soul Cairn, the player must be blooded as a vampire by Serana or be partially soul-trapped to gain access. Aside from these details, the quest lines follow a similar path to the Volkihar, but it diverges during the last story mission, when the player leads the Dawnguard's final assault on Harkon and his allies. The player and Serana succeed in killing Harkon in a climactic showdown, effectively eliminating the great vampire threat in Skyrim.