Anatomy of a Lovecraftian Space Creature For Your Old School Science Fantasy Campaign

Introduction 
I've been asked to go over the options for creating a child of the Lovecraftian stars. there are seldom more dear monsters to my hear then the creations of Lovecraft's circle of friends and fellow writers.  I started when I was thirteen years old when I discovered the works of HP Lovecraft in the back of a Famous Monsters of Filmland magazine. I haven't looked back since. The fact that Lovecraft's works are now in the public domain are icing on the cake.

Children of Azothoth 

 

Though out the centuries its really the Outer Gods that a space based game should really look at. The works of  Lovecraft detail quite a few of these gods along with their attendants. You can find most of these right HERE

 Recently Gorgon Milk featured a collection of the older Lovecraftian creations from the halcyon days of our hobby. Most of these were for 1st edition AD&D and OD&D. These can easily be adapted into your favorite retroclone with little to no problems at all.  you can find that over at his blog HERE

Aftermath of Goblinoid Games. 
 Last year Goblinoid Games came out with a fantastic Lovecraft book called Realms of Crawling Chaos and  I use it quite often to create any number of game monsters.
 

In many ways the book was a game changer because its take on Dark Fantasy broke the usual Chaosuim mold. Get that one right over HERE
The fact is that OSR produced another book along with this one that brought home some very dark fantastic ideas.  Yes this one.

 Carcosa was a game changer for me and gave me the opportunity to really get some weird stuff out there. Again its another that I'm still using. Get it right over HEREDavid Baymiller does his own versions of  some of the classic Mythos races and monsters. these are already set up and ready to go. You can find all of them on his page HERE 

Terminal Space also has the Mi Go as a playable PC Race HERE
It should not be forgotten that the 1st edition AD&D books had ton of Lovecraftian monsters that can be adapted to your game. Gibbering mouthers, mansized slimes, and much more are all from your AD&D Monster Manual And the Fiend Folio 1st edition. Go to town.

Ten Rules For Creating Lovecraftian Monsters 

1. The weirder the better. Players are going to each and every race that Lovecraft and his friends created. Design variations on all of the existing Lovecraft monsters. 
2. The verious mythos monsters existed in cycles of Earth's history. Be sure to slip one in of your own creation. There is a ton of room to adapt! 
3. These are alien races inimical to mankind. At best they should be avoided at all costs and at worst they will destroy your PC or change them forever. They're desires and actions shouldn't be understood by the players at all. 
4. Energy beings are completely dangerous and very unpredictable! Read the Colour Out Of Space! These beings infect anything that they encounter. They're going to always taint anything they come in contact with. Mutation checks and insanity should abound. 
5. Chaosuim and Call of Cthlhu set the standard for playing with the Mythos in rpgs but they've also created very rigid sets of creature rules. Break those tropes that players are expecting each and every time they encounter a deep one, shaggoth, or anything else. 
6. Each and every encounter with a Mythos monster should be memorable  There is no such thing as a minor Lovecraftian horror. Each and everyone is an NPC of very alien design. Don't be afraid to leave technology that PC's can't figure out or that kills out right. 
7. The PC's should be aware that any encounter with the Mytos means something. There isn't simply another deep one. There's a deep one because circumstances have forced them together. 
8. Insanity is a DM's friend! Don't be afraid to smear on the horror and depravity of the Mythos. Cults should be oozing it. Murder,body parts, problems are all run of the mill stuff when encountering the mythos.
9. Entities have cults and those cults are dangerous, murderous psychopaths that are  looking to kill your PC's. Don't be afraid to throw in a murderous cultist or three if it means more conflict. 
10. Mythos encounters  leads to more encounters in space. Because in space the final power is Azathoth and you don't want to piss it off.