It was not a vampire in the true sense, but a creature which gathered energy; much of that energy came from Time. Its main purpose was to seek and locate alternative sources of power for its ship. It had fallen through the same hole in the vortex as Varlos when he first hid on Earth.
Varlos had witnessed the Vampire's first attack, on Baron De Guerre. To conceal his own involvement he had assumed the identity of De Gaulle in the hope of hunting the creature down before it drew attention.
The creature continued to gather energy beyond its capacity. With the crew dead on arrival, the creature followed its sole purpose of gathering ever more energy. Without the means to discharge the energy, the creature became unstable. It was eventually returned to the vortex and its pain, loneliness and the madness it has known for so long was brought to an end. (PROSE: The Vampire of Paris)