One of the world's most powerful mutant telepaths, Charles Francis Xavier is the founder and sometimes leader of the X-Men.

Lockheed, a longtime companion of Shadowcat (Kitty Pryde), is a small purple dragon about the size of a cat.

When Nefaria attempted to escape Valhalla Base in a jet plane, Thunderbird leapt on board, disregarding Professor X's orders, and hammered the aircraft with his bare fists, causing it to explode.

Originally, Charles Xavier's training facility used traps, projectile firing devices, flamethrowers, and mechanical dangers such as presses and collapsing walls, but these were replaced by holographics, when the Danger Room was rebuilt using Shi'ar technology.

Magneto regards mutants as evolutionarily superior to humans and rejects the possibility of peaceful human-mutant coexistence, aiming instead to conquer the world so mutants (whom he refers to as homo superior) can replace humans as the dominant species. A Holocaust survivor, his extreme methods and cynical philosophy derive from his determination to protect mutants from suffering a similar fate at the hands of a world that fears and persecutes them.

Asteroid M has been destroyed and reconstructed by Magneto many times since it was first introduced. Each iteration has had several internal levels, including an observation deck, hangar bays and medical facilities.

When the X-Men discover Storm in the hospital with an injured jugular, Kitty guesses the truth: that she is the victim of a vampire. But Storm's teammates show faith in her, and she manages to break the hypnotic hold Dracula has over her.

Corsair is the father of Cyclops, Havok, and the supervillain Vulcan. He is also the leader of the Starjammers.

Department H is a branch of the Canadian government that sanctioned, supported, and monitored all superhuman activity in Canada. One of its early agents was Wolverine who was intended to be the leader Canada's own superhuman team, Alpha Flight, until he went AWOL.

When Phoenix inadvertently killed the inhabitants of an entire planetary system after consuming its star, the Shi'ar Empire sent its Imperial Guard to demand she pay with her life. The X-men vowed to protect her, but Jean's personality managed to take control and Phoenix committed suicide to ensure the universe's safety.