In the Blade film continuity, the Reapers are a mutant breed of Hominus Nocturna. The Vampire Nation conducted extensive research on their race's own genome, specifically the arbovirus that causes vampirism, in order to create a new breed of vampire free of the weaknesses common among their kind; silver, garlic, et cetera. Vampire overlord Eli Damaskinos subjected his own son Jared Nomak to this new vampirism virus, but the results were not what he expected. While Nomak did become immune to silver, garlic and even anticoagulant agents, he remained vulnerable to ultraviolet radiation and still could not walk in the sun. Worse still, the virus mutated and severely distorted Nomak's blood chemistry; he became more bloodthirsty than normal and needed to feed daily. Outraged that his father had turned him into what vampires would call a monster, Nomak fled the Vampire Nation and took to the streets, feeding not just on humans but vampires as well, turning them into what would become known as "Reapers".
The Reaper virus infects humans and vampires alike, turning them into Reapers within minutes of infection. Reapers can be easily distinguished from humans and vampires; those infected undergo clear physical mutations such as loss of hair and skin and eye pigmentation. The subject's mouth becomes radically altered; while vampires only grow elongated canines, Reapers' lower jaws split apart and stretch open into a hideous maw. Each mandible ends in a curved fang that secretes a paralyzing agent into a victim's bloodstream, preventing them from struggling whilst the Reaper feeds. The Reaper's tongue - a muscular tube ending in fine, sharp barbs - is used to suck the blood from a victim. The tongue's barbs carry the virus and inject it into the victim during feeding.
Reapers also possess a number of less visual mutations. An autopsy on a blood-starved Reaper revealed major alteration of the body's organs, making them appear radically different from human organs. The most noteworthy of these alterations was the heart, which had been encased in a shell of bone. The only gaps in the shell were a few small slits on either side which would be extremely difficult to penetrate.
With the exception of Nomak, the Reapers seem to lose much of their former intelligence, becoming savage and bestial. They do not speak and adopt a sort of pack mentality, hunting in large groups. They seem to be intelligent enough to understand Nomak and carry out his commands, though it is unclear as to how Nomak controls them. A likely possibility is that Reapers respond to different pheromones that Nomak secretes, allowing them to recognise him as an "alpha", a pack leader.
Reapers need to feed almost constantly. If they do not feed on human or vampire blood every few hours, they resort to cannibalism and will start to eat each other. Feeding on themselves appears to provide no nourishment, however, as Reapers have been seen eating the flesh of their own yet still succumbing to brain-death. Reapers that succumb to starvation do not disintegrate and their bodies remain intact but unable to function. During an autopsy, it was revealed that the body still tries to feed even after the brain has stopped functioning; a drop of blood was introduced into the Reaper cadaver's "stomach", which momentarily caused the other organs to pulsate.
Reapers are physically stronger than vampires and humans. They possess superior dexterity, reflexes and stamina and are also capable of adhering to different surfaces, allowing them to climb walls and ceilings like spiders. Unlike normal vampires, Reapers are not allergic to garlic and their flesh does not burn at the touch of silver. Their hardened skeletal structure allows them to shrug off gunshots and even precise strikes to the heart are difficult because the Reapers' hearts are encased in bone. Even the blood-thinner EDTA, which can cause vampires to burst like balloons, doesn't affect Reapers.
While immune to silver and garlic, Reapers are still vulnerable to ultraviolet radiation and cannot survive in sunlight. Ultraviolet rays will quickly reduce a Reaper to ash, as will piercing the heart if one is able to breach the small vents in the bony shell surrounding the heart. Aside from sunlight, the Reapers' only other major weakness is their own need to consume fresh blood on a frequent basis.