Blade's vampirized father plans to use him to fulfill a vampire prophecy. Manipulating them all is the Lord of Vampires himself, Dracula.
The vampires of Marvel Earth are part of the Mythos, being created by the Darkhold (the source of the Necronomicon), which was in turn created by Chthon, an Old One. The Darkhold not only has a spell which creates vampires but one that destroys them. Vampires have used the Darkhold to enhance themselves and Dracula, the Lord of Vampires, was himself destroyed and restored by the Darkhold, and has used it to increase his powers.