1d10 Lovecraftian Things Left Behind Table For Your Old School Space Opera

The basin ... was filled with a sort of viscous and semi-liquescent substance, quite opaque and of a sooty color.... [T]he center swelled as if with the action of some powerful yeast [and] an uncouth amorphous head with dull and bulging eyes arose gradually on an ever-lengthening neck ... Then two arms — if one could call them arms — likewise arose inch by inch, and we saw that the thing was not ... a creature immersed in the liquid, but that the liquid itself had put forth this hideous neck and head, and [it was now forming arms] that groped toward us with tentacle-like appendages in lieu of claws or hands! ... Then the whole mass of the dark fluid began to rise [and] poured over the rim of the basin like a torrent of black quicksilver, taking as it reached the floor an undulant ophidian form which immediately developed more than a dozen short legs.

—Clark Ashton Smith, "The Tale of Satampra Zeiros"

As the Outer gods move through system after star system there are often "things" that are immical to mankind and near man alike. These things have no mention in the bowels of books like the Necronomicon or the Formless Tales. They are merely beasts whose substance is another order of unlife clinging to the underside of the ancient things and waiting at the threshold to deal with your explorers and adventurers. 

1d10 Lovecraftian Things Left Behind Table

1. A strange insane thing of flesh, bone, and spirit that is actually an amalgam of the victims of the Outer God fused into a 3 hit point horror whose twisted acidic bearing limbs will strike for 1d4 points of damage. Its armor class if you can call it that is 9. 
2. This jelly like substance reacts as if it has intelligence and senses. It does not an merely parodies a real life form. The stuff will level drain a victim within 1d4 rounds of feeling its way across your flesh. The substance may be boiled down as a cure for certain mythos poisons. It must be snorted up the nose for its benefits.
3. This slightly radioactive mess clings to anything and will do 1d4 points of damage per round as it contaminates anything it comes in contact with for intensity level four radiation. Must be washed off with special herbal soaps. A very dangerous minor cancer that clings to the flesh of the Outer Gods. 
4. This proto shaggoth like substance will fill any body orifice and crack with itself. The thing will try to drown anyone within its substance. The monster is only 2 hit points and does 2 points of damage but it is insanely clever and dangerous in the extreme. 
5. This reddish disease like material moves of its own accord spreading Red Death and worse disease where ever it goes. Only fire will harm this 4 hit point thing of death and depravity. It likes to crawl through open windows. 
6. The Time Waster - This 4 foot long killer bag of pus and snot is actually deluded down time and space. The stuff will eat 1d4 hours of a person't life at a clip and only three hundred pounds of sand will harm the thing. It does not have hit points only years that will be shaved off of its substance. It has 1d20 years each time its encountered. 
7. Outer God Jelly This silver gold substance is the sweat and radioactive vileness of the Outer Gods. Left behind this 4 hit dice monster will want to feed and keep feeding until it breaks into a dozen smaller monsters. It attacks with pseudo tendrils for 1d6 points of damage. Only steel will damage its bulk. A very cunning monster it likes to hang out in pipes. Only fire harms it. 
8. Rolling Death. This black porous jelly rolls off of certain old ones and enters its victims through the ear channel and eats brains. The hit points depend upon the number of victims. It will start will 2 hit points and attack for 1d6 points of damage with its brain warping tendrils. Only the touch of certain rare earth metals will destroy it. 
9. A shaggoth from beyond. Double the hit points and attacks twice as fast. Very dangerous and very pissed off for being left behind. 
10. A blob of protoplasmic horror - This 4 hit dice monster is looking for victims to take over. The thing attacks twice per round and may mind control up to 3 victims at a clip. The thing has an armor class of 7 and exists in four separate alternative universes at once.