The story is loosely based on the Dracula story. Vlad was taken by the Turks as a boy to fight for them. He became the most fierce warrior known as the impaler. He escaped the Turkish army and his warrior ethos and became a prince in Transylvania where he got married and had a son. When the son of the Turkish sultan, the son who Vlad used to fight with, raises in power and picks up the plan to fulfill his fathers dream for a woldwide Turkish nation, the two are confronted with each other. In a way to gain the power to fight his former brother, Vlad becomes a vampire.
Of course we then get a bloody spectacle with many special effects and boring drama.