The alien creatures known only as the Bloodlines Parasites were a race of highly advanced and ferocious dragon-like beasts that came to Earth during the events of "Bloodlines".
The parasites hail from a Pocket Universe in which their race had extinguished all life, with the exception of a man known as Pax. Although seven parasites were originally sent in their spacecraft, only six crash-landed on Earth after "Slodd" was killed by Lobo and their hull blown open by him and Layla.
The parasites feed on human spinal fluids and were responsible for the deaths of hundreds of people before their defeat at the hands of the world's superheroes. Although the vast majority of people were killed by the Parasites feeding on them, a number of previously dormant Metahumans had the attacks activate their metagene, granting a sizable number of previously normal civilians with new-found superpowers. These individuals called themselves "New Bloods".
Ultimately, the Parasites sacrificed themselves to birth a creature known as "The Taker", a destructive monstrosity capable of spawning many more parasites and causing the death of entire worlds. Although the Taker defeated the majority of Earth's heroes with the exception of Superman, it was ultimately defeated by the combined forces of the remaining heroes and the "New Bloods".