|“||If you want an easier way to get a vampire's power, just let one of them turn you. If you're not tainted yet, you should be all good. But Eaters are different. Fouled. Trying to gain all of a vampire's powers, but none of their weaknesses. If Vampire Hunters actually existed, they wouldn't be dhampyr like in those legends. They'd be people like her—quick-thinking, underhanded, and determined to the point of annoyance.||”|
Eaters are humans who have eaten the flesh and ashes or drank the blood of vampires. Once they do so, their bodies undergo a sort of metamorphosis, and they acquire enhanced speed and reflexes - essentially becoming more like vampires than humans. Upon drinking the blood of just one vampire, Eaters gain the ability to sense nearby vampires, a power that actual vampires do not have. It appears that Eater-turned-vampires (such as Shizune Kijima) still retain this 'sixth sense' after they are turned.
The more vampires an Eater drinks from (and the stronger the vampires are) the more powerful the Eater becomes. However, an Eater's body is strengthened by their victims' power only up to a certain point. Too much, and the power will eat away at their bodies, their muscles and organs...though most might not sense the pain, it can build up little by little until it overwhelms the individual. (It should be noted that Theresia Riefenstahl has been spared this weakness after The Organization saw the power eat away at Rudi Wenders).
Gerhardt von Waldstein has theorized that when an Eater devours the flesh and blood of a living vampire, they gain the 'soul' energy that had filled the vampire's body. This is because "a vampire's blood is the catalyst that circulates the soul's energy through his body."
When a vampire drinks the blood of an Eater who's just drunk another vampire's blood, the first vampire will gain that vampire's abilities.
Eaters are utilized by both The Organization and its enemies, most notably in Vamp! IV, when the Sunford Clan sends out a horde of over two-hundred Eaters to combat members of The Organization. However, since the Sunfords had only bothered to give their Eaters (whom they view as slaves) the blood of one or two vampires each, the Eaters were fairly weak and no match for the members of the Organization.