I came up with this after watching the Blade movies and The Strain (which weren't made in the 80s, but are still good!) and wondering if it would be possible to make a dhampir character-type that would work within the rules and flavor of Gary Gygax's AD&D. I think it turned out pretty well.
Dhampirs: When a vampire mates with a human female, or alternatively when a pregnant woman is attacked by a vampire, the resulting offspring may have characteristics of both human and vampire, known as a dhampir. Such individuals are very rare and are almost always outcasts from the societies of both parents - viewed as abominations among humans, and as potentially-dangerous weaklings among vampires. Most are slain in infancy, and those who manage to survive to adulthood tend to be loners and rootless wanderers. They often become adventurers, and their racial characteristics (described below) make them particularly well-suited as foes and hunters of the undead.
Dhampirs may become fighters, magic-users, thieves (including acrobats), and assassins. Advancement is unlimited in all classes. Dhampirs may not be multi-classed characters, but those with sufficiently high ability scores may become a character with two classes, following the standard procedure. While a dhampir may be of any alignment, their natural proclivities urge them towards both chaos and evil, so a dhampir of any other alignment will face a constant inner struggle not to slide in those directions, making non-chaotic Good dhampirs and non-evil Lawful dhampirs almost unheard of.
Dhampirs have superior infravision, out to 90' range. They also have an instinctive, at-will ability to detect the presence of vampires (90% chance) or other undead (50% chance) within 90' range. Due to their sensitivity, dhampirs are able to track vampires as per a ranger of level equal to their own.
Dhampirs are totally immune to the charming gaze of vampires, and are allowed a saving throw vs. spells to resist the level draining effect of a vampire's attack (as well as other undead, though in the case of a level-draining attack from a non-vampire the saving throw is made at -4).
Dhampirs regenerate damage at a rate of one hit point per turn, including damage suffered from fire, cold, acid, electricity, and magic. Even if the dhampir has been "killed" by being reduced below -10 hit points, they will eventually regenerate and revive upon reaching a positive hit point total. Poison, system shock, death rays, disintegration, and other attacks that bypass regular hit-point-based damage, however, may still kill a dhampir. In addition, damage to dhampirs cannot be healed by any clerical (including druidical) magic, nor may they ever be raised from the dead, resurrected, or reincarnated.
Dhampirs may also recover hit points by draining blood from living victims. Due to their sharp fangs a bite attack from a dhampir inflicts 1-3 points of damage and an additional 1-3 points per round thereafter from blood drain, so long as the dhampir remains attached to the victim. One-half of all hit points drained thus accrue to the dhampir as healing (up to character's normal maximum hit points). This benefit is received from the blood of any living human, demi-human, humanoid, or animal, but the blood must be drawn fresh from the victim's body in order to be effective.
The downside of this ability is that dhampirs have an insatiable taste for blood that can cause them to lose control and go mad with bloodlust. At the sight of any freshly-let blood a dhampir must make a saving throw against spells or go berserk for 1-6 turns, attacking and attempting to drain any living creature within sight unless rendered immobile or unconscious. This saving throw is made at a cumulative -1 for each 24-hour period the dhampir has gone since last drinking fresh blood. Dhampirs do not require normal food or water on those days during which they are able to feast upon fresh blood.
Dhampirs are sensitive to sunlight and suffer the same negative effects from exposure to sunlight as per gray dwarfs and dark elves (as detailed in UNEARTHED ARCANA). In addition, after one turn of exposure they suffer one hit point of damage, and suffer an additional hit point of damage per turn of continued exposure thereafter.
Additionally, dhampirs suffer 1-4 points of damage per vial from holy water and +1 damage per die from attacks made by silver weapons. Damage suffered from exposure to sunlight, holy water, or silver weapons does not regenerate and can only be healed through ingestion of blood (as above). A dhampir reduced to -10 hit points or below by damage from sunlight, holy water, and/or silver weapons is permanently destroyed.
Dhampirs appear generally the same as humans, though they tend to have sallow or ashen complexions, regardless of their ethnicity. Their canine teeth are slightly elongated and their eyes emit a soft red glow in the dark (visible as a bright red glow to others with infravision, as with any other creature with superior infravision). Due to the fear and hatred with which they are treated by most other races, dhampirs will typically seek to keep their nature and origin hidden.
Strength: Minimum 15 / Maximum 18(00)
Intelligence: Minimum 3 / Maximum 18
Wisdom: Minimum 3 / Maximum 18
Dexterity: Minimum 14 / Maximum 18
Constitution: Minimum 11 / Maximum 18
Charisma: Minimum 3 / Maximum 14
Dhampirs feel towards other races the same as humans do
Dark elves (and half-elves of dark descent) are T towards dhampirs
All other races are H towards dhampirs (if recognized as such; otherwise they are treated as human)
Young Adult: 14-40
Middle Age: 201-300
Fighter: 12 + 5d6 years
Magic-User: 30 + 10d10 years
Thief: 18 + 5d8 years
Assassin: 20 + 5d8 years
HEIGHT: as human
WEIGHT: as human