You were a member of the Dawnguard, an ex-member of the Vigilance of Stendr, the the order collapsed at the hands of the vampire menace joining up became a no-brainer to you. A vampire woman had showed up at Fort Dawnguard, asking about one of your newest recruits who she claimed had freed her from her tomb, she was adamant she wanted to speak with this person. When Isran agreed to use the woman who became know as Serana as an asset for the Dawnguard, you viewed it as blasphemous to the cause, siding with a vampire? Unprecedented, unacceptable.

However, after fighting alongside Serana and the Dragonborn countless of times, Serana proved herself time and time again. You respected her, even if you viewed her very existence as infidelity. That respect turned Serana from an enemy in your eyes to an ally, and an ally whom you slowly began to view as a friend.