The Mi-go can transport humans from Earth to Pluto (and beyond) and back again by removing the subject's brain and placing it into a "brain cylinder", which can be attached to external devices to allow it to see, hear, and speak.
The Mi-go worship the beings Yog-Sothoth, Nyarlathotep, and Shub-Niggurath, among others, although their religious beliefs seem to have relatively minor importance compared to their scientific interests. Their moral system is completely alien, making them seem highly malicious from a human perspective.
One of the moons of Yuggoth holds designs that are sacred to the Mi-go. The symbols inscribed upon the moon are useful in various processes mentioned in the Necronomicon. It is said that transcriptions of these designs can be sensed by the Mi-go, and those possessing them shall be hunted down by the few remaining on earth .
Hastur apparently despises the Mi-go. His cult, servants of "Him Who Is Not to be Named", are dedicated to hunting them down and exterminating the fungoid threat. However, in the original story a human ally of the Mi-go mentions "Him Who is not to be Named" in the list of honored entities along with Nyarlathotep and Shub-Niggurath.
The Mi-go are also prominent antagonists in Pagan Publishing's Delta Green sourcebook for the Call of Cthulhu role-playing game. According to the guide, there are three castes: scientist, soldier, and worker. This raises the possibility that other castes may exist. The book also says that the Mi-go usually have five pairs of appendages though the number can vary up or down from that. Normally, the first pair is designed for grasping and manipulating, but in the scientist caste it is usually the first two pairs. The remaining appendages are used for locomotion. The soldiers may have two or more pairs of wings. Some individuals do not have wings at all if they are deemed unnecessary to their task. The Mi-go apparently can modify their own bodies. It is also suggested that all their external accouterments are actually extruded at will from the central gelatinous mass similar to the way the Shoggoth extrude body parts. In the Delta Green setting, the "Greys" are actually Mi-go.
They are distinguished by their mastery in various fields of science, especially surgery. Although they originate from beyond our solar system, they have set up an outpost on Pluto (known as Yuggoth in the mythos) and sometimes visit Earth to mine for minerals and other natural resources. The Mi-go normally communicate by changing the colors of their orb-like heads or by emitting odd buzzing noises. They can also speak any human language upon receiving the appropriate surgical modification.
The Mi-Go are also one of the main enemies of humanity in the role-playing game CthulhuTech, a game which combines Lovecraft's fiction with tropes and themes from mecha anime, in which their name is spelled Migou (see below); however, they are commonly referred to as "bugs" by humans. In this setting they are invading Earth because humanity has developed technology unknown to them, which combines Lovecraftian "magic" (actually advanced alien science) with advanced standard human mechanical and electronic technology, and created giant humanoid mecha for their military forces, and thus the Migou now perceive humanity as a threat, whereas before they considered humans as nothing more than a primitive species to be observed and experimented on. In a previous attempt to eradicate humanity (the First Arcanotech War) they used their knowledge of human genetics to create the Nazzadi, a genetically altered race of humans with jet-black skin and hair, red eyes, and sharp incisors (in an attempt to make them appear monstrous and alien to humans) and created a fictional history for the new race, telling them that they were an army of intergalactic conquerors and that Earth was their latest target, and only informing the oldest and highest ranking Nazzadi the truth of their origins. The Nazzadi later rebelled when the bulk of the race discovered that they were, in fact, genetically altered humans, and that they were killing members of their own species. The Nazzadi then allied themselves with the forces of Earth against the Migou, and were granted Haiti as a racial refuge (as the previous inhabitants had been all-but wiped out in the war.) This caused the Migou to invade Earth themselves (in the Second Arcanotech War), using their own non-humanoid mecha made using the advanced technology that humans had created, called "arcanotechlogy." The Nazzadi are loosely based on the Zentraedi of Macross and Robotech.
Here they are presented much as in the original Lovecraft stories, and somewhat similar to the way they are portrayed in Delta Green; being masters of science and genetics, and in particular human genetics. Their hostility to humanity could be seen as jealousy that humans had created a technology that they had never thought of, which then became outright genocidal hatred.
The Mi-go also appear in the final segment, directed by Byan Yuzna, of the movie Necronomicon .
A Mi-go is scripted to walk across the stage during the "Tentacles" number of A Shoggoth on the Roof, prompting Armitage to narrate it as "some horrible creature... I do not even want to know what that is".
It was of no use to demonstrate to such opponents that the Vermont myths differed but little in essence from those universal legends of natural personification which filled the ancient world with fauns and dryads and satyrs, suggested the kallikanzarai of modern Greece, and gave to wild Wales and Ireland their dark hints of strange, small, and terrible hidden races of troglodytes and burrowers. No use, either, to point out the even more startlingly similar belief of the Nepalese hill tribes in the dreaded Mi-Go or "Abominable Snow-Men" who lurk hideously amidst the ice and rock pinnacles of the Himalayan summits. When I brought up this evidence, my opponents turned it against me by claiming that it must imply some actual historicity for the ancient tales; that it must argue the real existence of some queer elder earth-race, driven to hiding after the advent and dominance of mankind, which might very conceivably have survived in reduced numbers to relatively recent times — or even to the present.