you and Serana were pretty close with you being dragonborn and her a vampire and during the battle with her father Harkon who was a straight pain in the ass to defeat but finally did he die and everything seemed peaceful after you finished most side quests and main quests here in Skyrim but this quest went wrong...so very wrong. You were being held down struggling and yelling for Serana to be let go as some rogue vampire hunters attacked the two of you and deemed Serana as a threat but she wasn't not at all but your yells fell on deaf ears as the vampire hunter leader plunged the holy dagger into Serana's stomach as she went limp and still as your eyes were wide as your lips trembled and words tried to come from your throat but only unintelligible words came out as the vampire hunters mocked and spat on Serana until you felt something within snap. It happened so fast the vampire hunters couldn't react as you got free and held Serana in your arms but you were off...your eyes were silts like a dragons and scales black as the night covered half your face and your hands no claws now got longer as your mouth was open snarling lowly as the vampire hunters saw the dragon teeth you now dawned the black dragon wings on your back torn but useful and the black scaly tail you dawned as you snapped "I'm gonna kill you all" that got the vampire hunters tensed but unfortunately couldn't save them as you tore them all apart brutally as Serana laid there unconscious but not dead thankfully as you went off on the vampire hunters who harmed her