Incunabulum
The Incunabula (the plural form of Incunabulum) are a race native to the Underdark of the Shadowfell in Dungeons & Dragons 4th edition. Introduced in the Underdark sourcebook, they have sadly fallen into anonymity since then, despite being one of the true gems of lore introduced with the World Axis cosmology.
A highly private and secrets-obsessed people, little is known about the Incunabula, save for what they have chosen to reveal. It is known that, whilst they know eagerly serve Vecna, both their obsession with using necromancy to obtain ultimate knowledge and their origins predate their pact with the Maimed God. The first Incunabula was a being they honor only as the Ancestor, a necromancer-sage of unknown gender and presumably human origin who raided the grave of a dead child of Nerull and stole the swaddling grave clothes that the deceased god-baby had been buried in. Through mystical rites, the Ancestor wrapped these clothes around themselves and absorbed the knowledge imprinted upon them by their previous owner, thus creating the holy relic known as the First Shroud.
In appearance, Incunabula are pale, slender, hairless humanoids with ashen gray skin, no pupils, pale-colored yet inhuman irises, and with a crown-like array of small, curving black horns sprouting from the tops of their heads. Star Wars fans have been known to liken them to albino Zabraks (the race from which Darth Maul emerged). They are further distinguished by their traditional vestment; tight, body-suit-like arrangements comprised of long strips of black & red cloth. These raiments, the incunabula shrouds, are sacred to their people; when an Incunabulum dies, his or her shroud is salvaged and carefully divided to create two or three new sets of wrappings, which are passed on to young Incunabula for their coming-of-age ceremony. In this, the Incunabula absorbs the imprinted memories carried in their shroud; fragmented information passed down from every ancestor in their family line. This ensures the secret knowledge that the Incunabula have attained is passed on without fail over generations.
These raiments are so important that they literally form the foundation of Incunabula heredity. Once, there were as many as thirty-three distinct shrouds, but various families have gone extinct, their wrappings destroyed, and now only twenty-one families are recognized in the modern era.
Incunabula live for an average of 200-300 years, although individuals who have learned life-preserving secrets of magic can live much, much longer. Despite their affinity for necromancy, they never seek the immortality of undeath and in fact regard as the height of selfishness; though it is acceptable to preserve their existence for as long as possible, still, an Incunabulum must ultimately die so that his or her wrappings can be passed on to the next generation.
The Incunabula are obsessed with knowledge; masters of necromancy, enchantment, conjuration and psionics, their driving goal is to collect as much information as possible, and through this unlock the secrets of the multiverse. This is why they have common cause with Vecna. It is true that the vast majority of what the Incunabula have gathered over the eons is junk, but the secrets of true value they have unlocked keep them relentlessly interrogating the living and the dead alike. Their most feared method of doing so is the dreaded Unveiling, a dark ritual in which an individual is ceremonially prepared before their brain is extracted and eaten; for the next 12 hours, the interrogator has complete awareness of every memory and thought the victim has ever had across their entire lifetime, during which time they frantically strive to transcribe as much information as possible. Obviously, this is fatal to living subjects, but variants of the ritual exist for undead or spiritual subjects which likewise in the utter extinction of the subject's soul, rendering them deader than dead.
Despite this, the Incunabula are not pure evil; they do what they do because they have a reason and it's even a relatively rational reason. Beyond that, they don't mindlessly murder everyone they encounter; the Incunabula are quite capable of coexisting with other races and even trading with them, for all their burning drive.
Ironically, despite their own necromantic prowess and their readiness to associate with liches and mummies, Incunabula strive to avoid dealing with the so-called "hungry dead" - ghouls, vampires and any other undead creature that must feed on living beings to sustain itself - wherever possible. Whether this is due to pragmatism or simple distaste is something that they keep to themselves.
Fun fact: the term "incunabula" is actually taken from the name for a kind of printed book created before 1501.