The Birth: The Inhumans are a separate race of beings and should not be considered as mutants. They are not even human! Each being has a different power. Originally, they inhabited the city of Atillan on Earth, but when the city was destroyed moved to the moon, and then to the acient city of Atlantis. The first of the Inhumans, Medusa, was introduced in The Fantastic Four #36, Gorgon was introduced in The Fantastic Four #44, and the rest in issue #45. The had a 12 Issue series of their own, The Inhumans from 1975-1977.

The Legend: The Inhumans have always been storng allies of the Fantastic Four. The Inhumans are rules by the Royal Family and the population is controlled by the Inhumans Genetic Council. However, the Genetic Council hasn't been as friendly to the Fantastic Four as the Royal Family.

....... Black Bolt
Black Bolt is the Inhumans' King. With the fork shaped antenna on his head he is able to control electrons and communicate with Medusa. He is also immensely strong. He is unable to speak, because his merest whisper would cause an incredible destructive force, which he has had to use on occasion.

....... Medusa
Medusa is Black Bolt's wife, the Inhuman's Queen. She is able to manipulate her hair and use it to lift heavy objects, and stretch it for quite a ways. She was originally a member of the Frightful Four (along with the Wizard, the Trapster and the Sandman), and first appeared in Issue #36. She joined the FF in issue #130, filling in for Sue when she left the team.

....... Crystal
Crystal is Johnny Storm's (the Human Torch) one time girl friend, and a fill in member of the Fantastic Four, filling in for Sue when Sue was pregnant, and once again when Sue and Reed left the team (Issue #305). She was wed to Quicksilver in issue #150, and had a daughter by him; named Luna. Somewhere along the line Quicksilver turned evil and left his daughter and wife to fight against the Avengers and the Fantastic Four. But afterwards, he returned to his wife in Fantastic Four Annual #21 saying that he had been a victim of Maximus.
Crystal has the elemental power, the ability to control the four elements : fire, water, wind, and earth. There was also a pretty unnecessary fight between her and Sue in issue #332.

....... Gorgon
Gorgon's power is his ability to create an immense destructive force with his kick. He was introduced in Fantastic Four #44 when he came searching for Medusa.

....... Karnak
Karnak is Crystal and Medusa's cousin. He is able to find the weakest point in any object, and then destroy it.

....... Maximus
Maximus the Mad is Black Bolt's brother, and he claims to be the rightful heir to the Inhuman's throne. While the Inhumans still occupied Attilan, Maximus created the Negative Barrier around the city, which allowed nothing, including air, to enter or exit. The Negative Barrier was destroyed, along with Attilan when Black Bolt spoke.