Aliens: Space Strigoi

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Space strigoi are particularly devious, shapeshifting space vampires that leech lifeforce from other sentient beings. They are phasic in nature and feed off the psionic energy of their victims. They resemble hideous, fluorescent-skinned goblins that can disguise themselves  as attractive humans (1d6 rounds), near-humans (1d10 rounds), a variety of small, pet-like animals (1d4 rounds) in order to lure their prey closer. They need a round to rest in native form between adapted forms.

Space strigoi have redundant anatomy--two pulmonary systems, two two metabolic systems, and several neural nodes throughout their body to enhance brain and coordination functions--making them quite difficult to kill. This unique physiology allows them long life of several millennia.

In order to be completely put down they must be disintegrated whole. Dismembering will only trigger regeneration and piss them off.

Stats:
AC 18
HD 3d12+2
THB -1
ATT (see below)
ST 17
MV 5
XP 500

Psionic Leech
Space strigoi will sap the lifeforce from their prey via psionic attack. They must be within 1 area in order to siphon the life energy of a given target at a rate of 1d4 HP plus 2 PRE per round. Drained victims will become empty husks that will revive in 1d8 rounds and rise as hungry strigoi at half the hit dice of their "parent".

Molecular Rearrangement
Strigoi can reorganize their own bodily mass to shapechange into any creature they have personally touched. Often they choose the guise of an attractive humanoid or a cuddly or wounded pet. Their ability to alter their molecular makeup also allows them to "phase" through solid matter (e.g., a ship's bulkhead), though this takes extreme concentration and can only perform the feat twice per day.

Regeneration is another ability gained by controlling their own matter. They appear ageless even in their native form and may regrow limbs and even a head with brain in 1d12 rounds.

Detect Lifeforce
They have an innate ability to locate sentient beings or creatures of sufficient psionic energy from which to feed. This is automatic and they will likely target those closest or most vulnerable.

Psionic Invisibility

They may make themselves "invisible" to those around them by way of a mental block. For this reason they often do not appear in person except to their immediate victim, but can be captured as a non-identifiable florescent blur by electronic recording devices. 

Psionic Grasp
Strigoi can lure their prey through psionic manipulation resembling seduction. Victims will obey the vampire so long as they fail a Presence (PRE) or comparable attribute save with a -1 handicap to their roll.

Goblin Form - Claws & Fangs
In their native form they can bite and scratch with 1d6+1 and 2d4 damage respectively.

Rumors from the Reaches (for GMs)

• Space strigoi will try to set up a lair in an uninhabited corner of a spaceship, space station, or other stellar craft. They will often lure victims to the lair and hold them prisoner through Psionic Grasp for later feedings. 
• Space strigoi who are not completely vaporized should be flushed into space through an airlock to prevent them from regeneration and claiming more lives.
• Space strigoi are highly intelligent and have in-depth knowledge of spacecraft mechanics and technology. They will often disable propulsion, communications, and emergency escape systems to prevent a pool of potential victims from escaping.
• Space strigoi can enter a hibernation phase and persist for eons in interstellar space until found by unsuspecting travelers. 
• Space tramps, smugglers, and cowboys are prone to tell tall tales of strigoi encounters, but are also more likely to be superstitious and hang all manner of emblems and graffiti strange written characters on their vessels to ward off the dreaded space vamps.

Sources

• Wikipedia article as inspiration
• OSR inspiration