Quests are tasks set for the Dragonborn to perform in The Elder Scrolls V: Dawnguard. In total, there are twenty-two quests featured in the add-on. Twelve are featured in the main quest, with several optional side quests.
The first quest can be started at level 10 or above by listening for rumors or asking Hold Guards about a group of vampire hunters who are recruiting. This will steer the Dragonborn in the direction of Fort Dawnguard and the add-on will begin. Alternately, the questline can be started as early as level 1, directly after escaping Helgen, by going to Fort Dawnguard via Dayspring Canyon and interacting with the applicants and Dawnguard members.
During the quest "Bloodline", the Dragonborn must decide whether to continue assisting the Dawnguard or join Harkon and the Volkihar Clan. Choosing the path of Harkon opens the Vampire Lord skill tree.
Once this questline has started, periodic attacks by vampires on cities and settlements the Dragonborn visits will begin, which can result in the death of various characters, such as merchants, quest givers and other important unprotected characters. To prevent these deaths, it is recommended to reach at least the "Bloodline" quest in the story, after which the attacks will subside.