Picture by Tom Sullivan, taken from S.Petersen's Field Guide to the Cthulhu Mythos.
"It was red and dripping; an immensity of pulsing, moving jelly; a scarlet blob with myriad tentacular trunks that waved and waved. There were suckers on the tips of the appendages, and these were opening and closing with a ghoulish lust.... The thing was bloated and obscene; a headless, faceless, eyeless bulk with the ravenous maw and titanic talons of a star-born monster. The human blood on which it had fed revealed the hitherto invisible outlines of the feaster."
—Robert Bloch, "The Shambler from the Stars"
The star vampire dwells in outer space and is characterized by its ravenous appetite for blood. The creature uses its enormous talons to capture its prey, grappling and crushing the unfortunate and then draining the victim's blood through its tubular suckers. It is normally invisible, but following a sanguine repast, the star vampire becomes temporarily visible from the undigested blood it has absorbed.
The monster is always accompanied by a sardonic, preternatural titter which heralds its imminent arrival and marks its presence, even when it is invisible. After it has fed, the star vampire quickly departs, the eerie, ghastly laughter following in its wake. The occult book De Vermis Mysteriis (or Mysteries of the Worm) contains a spell for summoning the creature; though doing so is often dangerous, as the thirsty star vampire is likely to feast on its caller.
Source: Howard Philip Lovecraft Mythos. Bloch, Robert  (1998). “The Shambler from the Stars”, which was originally published in the September 1935 issue of Weird Tales. Tales of the Cthulhu Mythos, 1st ed., New York, NY: Random House. ISBN 0-345-42204-X, Petersen, Sandy (1989). “Star Vampire”, Call of Cthulhu, 4th ed., Oakland, CA: Chaosium. ISBN 0-933635-58-3.