The Eight Immortals are a team of superheroes based in China in the Marvel Universe, first appearing in the X-Men comics.
History
When the X-Men rescued the mutant Xorn from a Chinese military facility, they encountered the Eight Immortals who were their to stop them. They revealed that they had been chosen to protect China, though it did not appear that they were a government sanctioned team of superheroes as was the norm in China (e.g. the People's Defense Force, Dynasty, and the Ascendants). After the X-Men refused to turn him over, the Eight Immortals attacked the X-Men.
They were holding their own against the X-Men, both sides winning and losing some fights until Gambit was blinded in his fight with one of the members. Havok then cut loose, temporarily knocking out the Eight Immortals and cracking the containment helmet that Xorn was wearing. Which destroyed their X-jet as it was sucked into the black hole. Realizing that the X-Men were innocent of the earlier devastation done at the military facility as it was the evidence pointed toward Xorn, they decided to assist the X-Men.
Unfortunately elements of the People's Liberation Army led by the Chinese state sanctioned superhero, the Collective Man appeared. They saw the X-Men as a threat since their presence in China was unauthorized and did battle with the X-Men. Eventually the Eight Immortals were able to guide the X-Men to safety, taking them to a military base where the X-Men "borrowed" an aircraft and left China.
Powers and Abilities
All of the members of the team appeared to have training in the martial arts. Several of them have body armor and/or weapons (hammer, swords, handgun, etc). At least several members also have superhuman abilities though it's not clear if they are mutants, have been mystical powers, etc. The female was able to manipulate the vegetation to attack. One of them was able to weaken Polaris from a distance, making her feel as if she was dying and causing her to collapse. Another one either had superhuman strength or his two swords were the cause of his abilities as he was able to deflect the ice blasts sent his way by Iceman and when he was finally completely encased in ice, he quickly broke free by shattering the ice.