Whisperer in the Outer Darkness
I see this as the "second" episode of the season after the two-parter "The Stars Are Right" that introduces the Cthulhuoid Horrors we share space with.
The crew gets new orders from Starfleet. They are to pick up a professor Alyson Wilmarth. While setting up a new subspace relay on Pluto the Starfleet Corp of Engineers uncover two startling discoveries. The first is the remains of a Tellarite survey team that dates back to the early 20th Century, circa 1930-31. The second is what the Tellarite's were investigating. The remains of a small outpost of any unknown civilization that dates back to 12 million years ago. Among the remains are a frozen Danuvius guggenmosi, a human ancestor from the Miocene. Artifacts from the civilization bear a resemblance to other artifacts found on Earth in the Andes, Appalachians, and Himalayas mountain ranges. Dr. Wilmarth is an expert on these.
Naturally, Starfleet contacted Tellar Prime about this to see what they knew, and maybe figure out what they were doing on Pluto in the 1930s. This puts Dr. Wilmarth in contact with Dr. Akeley, her counterpart in the Tellarite College of Exoarcheology. Dr. Wilmarth was scheduled to take a sabbatical and head to Tellar Prime when the term was done. Dr. Akeley, in typical Tellarite fashion claims he can't wait for her and takes their data and heads out to a remote system he thinks has the answers.
Once on Tellar Prime, we learn that the Tellarite name for Pluto is Yuggoth, though they claim that name was not one they made up, but what they were able to decipher. Much like Earth, there is evidence of this unknown species having lived on Tellar Prime, the 5th planet on the 61 Cygni/Tellar system. The Tellarites wanted to know how artifacts from Yuggoth got to Tellar Prime.
The crew, with Dr. Wilmarth still in tow, head out for the remote system discovered by Dr. Akeley.
<<I'll add some bits about getting to the planet, the tech on the planet here.>>
They discover Dr. Akeley, but he is acting with a flat affect is very polite to everyone (should be a dead giveaway that something is wrong). He claims to have been in contact with the civilization, the Mi-Go, and they are friendly and only wish to share their secrets of over 70 million years of space travel with the Federation. Akeley of course has stayed hidden in the shadows this whole time. When he is confronted they will discover the entire back of his skull has been opened and "scooped" out. His brain and eyes are gone. The look is similar to the original Tellarite masks on The Original Series that made their eyes look like they were missing. Only a tiny device is left in his otherwise empty skull. It is apparently "piloting" the body.
Here the ship is attacked by Mi-Go. They can't appear on sensors and are only known by the gravity they displace when they land on any deck with artificial gravity.
I am certainly going to use some ideas from Forbidden World even if it is just to model a Mi-Go creature from the movie poster. I like the idea of a human/Mi-Go hybrid that can talk. Maybe it will have Dr. Akeley's or even Dr. Wilmarth's face. Recreate the poster art, but not the movie, Galaxy of Terror.
I still need to come up with a resolution for this. What do the Mi-Go want? How does the crew "defeat" them? Still need to work out those details as well.
This will be a good test of Star Trek Adventures mixed with Achtung! Cthulhu 2d20 both from Mōdiphiüs.