The vampires are a non-sentient hominid species of the Ringworld.[1]
Described as having very white skin, with silver hair and slender bodies. They are pretty, with fine chiseled features, even male vampires are more pretty than handsome and beardless. Their heads are smaller than humans'. They wear no clothes.[1]
Descended from Pak breeders, the vampires didn't develop sentience like other Ringworld hominids, instead they have developed a powerful release system of hominid sex pheromones that causes in other hominid species a crazed urge to mate with the vampires. During the interspecies mating act the vampires sink their teeth in the victim's neck and start feeding on their blood, killing them.[1]
By 2881[2], the vampires are largely extinct, at least on the environs of the Machine People Empire, but some are kept, tamed and with their teeth pulled out, by older people for sexual purposes. Occasionally some of these vampires may escape and establish wild population, such as the one encountered by Valavirgillin and Louis Wu.[1]
The City Builders keep and use vampires to make a perfume out of them that is used while engaging in rishathra with other species.[1]
While vampires aren't sentient, a vampire that is exposed to the tree-of-life root and consumes it will become sentient and highly intelligent as it evolves into the protector stage as demonstrated by Bram.[3]