this is challenge that I've never seen before
basically your character is the dragonborn but you are a vampire not necessarily a vampire lord but a vampire and have been around since at least the oblivion crisis one day you are crossing the border doesn't matter which one and the empire captures you along with ulfric stormcloak you wake up in the back of a carriage and from their you journey starts and to clarify you do not know you are dragonborn until the whiterun fiasco
the pairing of this story is dragonborn x serena