The Thing, obviously, but the timing seems off. The Thing was released in the UK in the summer of ’82, this appeared in White Dwarf in December 1983. Maybe I watched it on home video, then a technology in its early stages, but as I’m such a stickler for the cinematic experience – and was a fan of John Carpenter’s work – that’s a little unlikely. Another mystery whose answer is lost in the murk of memory.
I based my version of the creature on one interpretation of what’s going on in the movie. In the original 1938 short story by John W Campbell it works a bit differently, devouring and imitating prey rather than infecting them. Take your pick. In the absence of a name for the species I called my version the "jesmai", probably as a riposte to Jamie (who edited WD) for insisting that I give it a name at all. But all Campbell tells us is that it is
When attacking they grapple their opponent and then, if successful, lash out with a razor sharp proboscis hidden at the back of the creature's throat. Damage done by the proboscis is determined solely for the purpose of puncturing armour – the victim takes no actual damage as the proboscis only penetrates a centimetre or so, but a venom with potency equal to the Jasmai's CON is injected.
If the venom overcomes the victim's CON they black out and must roll CON as a percentage to come round. This roll is attempted at the end of each round until the character recovers. After recovering, the character experiences no ill effects from the venom for 2d6 days, whereupon they will suddenly lapse into a terrible fever characterized by alternating bouts of sweating and uncontrollable shivering. At this point the character can still be cured with a Dispel Magic 8, but if the fever is allowed to progress then the character lapses into a coma within 1d4 hours and then loses their own identity as they transform into an exact duplicate of the creature that infected them. The transformation takes one hour and can be reversed only with Divine Intervention.
At the end of the transformation the character will have all the skills, memories and motivations of the original creature. The character's own soul/ identity has been destroyed.
The creatures can be distinguished from humans when cut. Instead of bleeding they exude a greenish sap, and the inside of the body is a homogeneous pulp without bones or organs. They take 1d3 CON damage per full turn for every 10° Celsius above freezing.