Vampires

The girl tripped him expertly. He landed face down, rebounded, and tried to crawl away on all fours. But she was already kneeling besides him, one arm wrapped around his neck. Doran's body felt numb all of a sudden. Had her long black fingernails just scraped against his skin? He wasn't sure anymore; he tried to grab her wrist, but his fingers wouldn't bend. There was a weight on his back, and a piercing pain somewhere below his ear, but even that felt distant. He couldn't tell how much time had passed.
— Vryheid

No, they're not undead. There's no such thing as undead. Vampires are very much alive, needing food and water (not to mention air) in addition to about half a liter of blood a week in order to survive. That's fresh human blood; they can survive on refrigerated or animal blood, but the farther from the ideal it is, the more they need. The origins of vampires are unknown. Most commonly they are explained as the result of a new brand of medical nanobots, gone wrong. On some worlds they are deemed to be a myth; on others, they do their level best to stay hidden, on pain of being hunted down and killed. In a few places they can even live in the open, getting what they need from blood banks or farms. Vampires can't get sick, and they heal from any injuries much faster than baseline humans. They also don't age, and with enough blood they can also grow younger, down to 17 years old. As long as they get more blood than the absolute minimum, they also manifest superhuman speed (though less than Cyborgs) and strength (but less than Genemorphs). In the way of downsides, a vampire's skin and eyes are very sensitive to natural sunlight (unless it's a colder sun -- class K or M), so they need to be well-protected going outside by day. If deprived of blood, they first develop uncontrollable thirst for it. After two or three weeks they also begin to age rapidly, and at the end of forty days or so enter a form of suspended animation that allows them to survive for years. If a vampire's nanobots are somehow deactivated or destroyed, they start aging fast, and die soon unless regen treatments can be applied. If they survive the system shock, that makes them baseline again. A baseline human or genemorph can turn vampire in days, simply by getting a significant amount of vampire blood in contact with their own, for example through a large open wound, or outright transfusion (vampires have blood type O). That can happen at any age, but teenage or younger people are at risk of complications. Vampire nanobots are incompatible with cyborg nanobots and will destroy each other if mixed, killing their owner.

Civilization and Culture

Common Taboos

Because many people mistrust or fear vampires even in cultures where they're otherwise accepted, they have a strong taboo against entering somebody's home uninvited.

Genetic Ancestor(s)