Great Vampire
The Great Vampires were gigantic humanoids in Gallifreyan legend that lived during the Dark Times.
Biology
The Great Vampires were colossal humanoids with grey skin and wings. Like lesser vampires, Great Vampires needed blood to survive, but their large size dictated they needed considerably more. Great Vampires were extremely powerful and one individual could drain a whole planet dry. They could absorb energy in almost any form and survive numerous minor wounds. The only way to kill one was to stab them through the heart, usually with a steel bolt. More powerful Great Vampires needed to have their heart fully destroyed in order to kill them. (TV: State of Decay)
Their appearance could cause hallucinations, in which they could appear as horrible, huge, winged snakes with many eyes. (PROSE: The Pit)
History
The Great Vampires suddenly appeared in the universe, causing mass destruction and chaos, (TV: State of Decay) having been accidentally released from their dimension into the universe by the Time Lords. (AUDIO: Project: Twilight)
According to a transmission which Samantha Jones received on Anathema (and which may have been influenced by Faction Paradox propaganda), the Great Vampires came into the universe when Rassilon first opened a black hole in an attempt to draw power from other planes of existence. The black hole reached through to an inhabited plane, and monsters with great leathery wings and batlike heads swarmed through the opening. (PROSE: Interference)
The Great Vampires rampaged through the cosmos during the Dark Times, (TV: The Infinite Quest) and eventually created Earth's vampires (PROSE: Vampire Science) and the Saturnyns. (PROSE: The Multi-Faceted War)
The ferocity and resilience of the Vampires made their defeat very difficult, even for the Time Lords. Conventional weapons were virtually useless. Rassilon ordered the construction of bowships to exploit the one weakness of the Great Vampires — their vulnerability to being impaled through the heart. ((TV: State of Decay) He may have just taken credit for the bowship idea, which was in reality invented by someone else. The outlets to the Vampires' universe were blocked and reinforced by forced-matter shells disguised as planets, including Earth.
Eventually, all but one Vampire — the swarm leader — were found and destroyed. (PROSE: Interference) This sole survivor escaped into E-Space, using his great power to draw the ship Hydrax with him. He turned the three humans on this ship into vampires to feed and serve him for a thousand years until the Time of Arising. As he rose from the ground, the Fourth Doctor used a Scout ship from the Hydrax to pierce his heart, killing him. (TV: State of Decay)
An alternate perspective
In a TARDIS projection during the Eighth Doctor's infection with anti-time, the head of the Arcalian Chapter Houses, Provost Lord Tepesh, revealed himself as a Great Vampire in disguise, even saying he was a direct descendant of the King Vampire. Tepesh claimed the Great Vampires were a peaceful lot, content to drink the blood of non-sentient, genetically bred cattle, until Rassilon showed up, declared the Vampires should not be allowed to exist, and began a 500-year war of extermination. (AUDIO: Zagreus)
Alternate timeline
During one of Romana II's, Leela's and Narvin's trips to alternative Gallifreys, they visited one where Rassilon was killed by the Great Vampires after completing the transduction barrier. The Vampires then darkened the barrier to block out all light so they might live safely on Gallifrey. Over the next millennia the vampires gradually took over the True Lords, until the battle between the vampire Lord Prydon and the True Lady Magestrix Borusa. During this battle, with Leela's help, Narvin and Romana helped Borusa and recaptured the Transduction barrier, increasing the light levels allowed to pass through and destroying the Vampires. However, this made Romana feel like she was becoming a "Destroyer of Worlds" as according to her she had killed the Vampires and the Time Lords of her universe. (AUDIO: Annihilation)
Behind the scenes
According to Doctor Who: Creatures and Demons, a source this wiki considers invalid, the Plasmavores are believed to be descended from the Great Vampires.