There must have been something in the air or the water of the world of 1951 because this classic was released along with a whole bunch of other sci fi classics.
According to wiki :
The plot line goes something like this according to wiki :
Using the Man From Planet X For Your Retro Science Fantasy Gaming
At first glance there doesn't seem like there's a lot that can be done with this film. Actually there's lots to mine here. The whole isolated Scottish village plot could be used as a simple one night Rpg con adventure set. Quick easy stat up for all of the villagers and the man from planet X himself and your ready to go.
Using The Xians in any of the retroclone games is a simple matter. The greys from X-plorers are a great stand in. Simply convert over the language to a music base and your in business. For Swords And Wizardry it would look something like :
Man From Planet X (Scientist/Warriors )
Armor Class: 6 (13)
Move : 9
Stars Without Number has the Grays also built right into the system. This race could show up in Mutant Future very easily and be conducting experiments on mutants,recovering relics for scientific study, or planning another invasion.
The Prometheus Option
This poster recently showed up on the internet and has become a viral bug during the hype leading up to the movie. It does present a very viable option that wasn't explored in the movie. Since "The Man From Planet X "was the advanced scout for a coming invasion because his planet was dying then its reasonable to assume that its still out there. The race has advanced anti gravity and black hole technology allowing it to roam the universe in search of viable planets to invade.
If the race is gone then it stands to reason that a scientific exploration mission to explore the mega dungeons of this world might be an option. The technological cache would immense. The value incredible but you'd better have a scientist/bard with your party since all of their technological and language is musically and mathematically based. There might also still be members of the race in stasis waiting for another opportunity to invade. There are many options for this race in the coming campaign as well.
There could well be pissed off survivors on Planet X still searching for another colony world to conquer and conduct their mad scheme of mind control madness