300 isn't a DC comic. It has its own independent creation and doesn't fall under the DC Comics universe. The story and characters are distinct from DC's offerings.
Some fanfictions pair Azrael with a human who has a special gift, like being able to see the future or communicate with spirits. This human can act as a guide for Azrael in the human world, while Azrael protects the human from the more dangerous aspects of the supernatural world.
Vampirella wasn't a DC comic. She has her own independent comic series and background separate from DC's universe. DC has its own array of characters and storylines that don't include Vampirella.