Star Vampires

Star Vampires are normally invisible, their presence signalled only by a kind of tittering sound. After feeding, they become visible through the blood they drink.

In the RPG...

A Star Vampire's primary trait is that it's invisible, so any attackers take a Penalty Die. After feeding, however, the blood in their system makes them partially visible for 6 rounds, during which time no Penalty Die is needed. They also have 4-point armour, and bullets only do half damage—though I'm not actually sure if this is before or after the armour deduction. Though they can strike at a victim with their tentacles, their primary method of attack is a seizing maneuver whereby they hold the victim and drain their blood, losing an average of XX STR per round.

    The only stat which has been changed for the 7e Malleus Monstrorum is the Vampire's STR. It retains its average of 130, but has been given a much wider range—80-180 vs 55-205.

In a video game...

Star Vampires would be pretty cool in a video game, I think. Hearing a tittering, but not being able to see what was making it would be pretty scary on its own, but then for someone to get attacked and suddenly see the invisible monster as it engorges on blood would add some great horror.

In a film...

Just like in a video game, the imagery of a blood-engorged monstrosity would be great to see rendered on screen.