The H'yulthri
AKA: The People
First Appearance: Iron Fist 2 during a flash-back to Danny's first adventure as the Iron Fist.
Died In: An entire generation of H'yulthri was wiped out in Power Man and Iron Fist 75. Between Iron Fist, Namor, Wolverine, and the poisoned ground of K'un Lun, most of the next generation met a similar doom. However, as Master Khan has pointed out, as long as H'yulthri seeds remained, the race will survive. Thus the H'yulthri may rise yet again to plague K'un Lun and (when they can get to it) the outside world.
What's Their Problem? According to the H'yulthri themselves, they were there first and initially welcomed the human settlers of K'un Lun with open fronds, but were met with fire and death. Given their need for animal protein to nourish their podlings, their insistence on referring to humans as an "infestation," and their interest in expanding into worlds outside of their own dimensional anomaly, I'd have to question the sincerity of their account...
Powers: They're plants. They grow like crazy, which is more dangerous than it sounds since they can completely terraform their surroundings into habitat unsuitable for the survival of anything in the animal kingdom. They control various herb-based narcotics that can knock folks out or control their actions; thus they've been able to take over the bodies of Lei Kung and Wolverine, even while the minds of those strong-willed individuals fought for control. They can even make themselves over into passable humanoid copies, as one plant-based simulacra of Iron Fist did for the last five issues of Power Man and Iron Fist.
Heroes They Keep Running Into: The H'yulthri have had repeated confrontations with Iron Fist; Danny led the expedition that wiped out one generation of their species (much to Power Man's dismay, who thought everyone was taking six foot talking plants just a little too seriously). Dr. Strange slammed one dimensional doorway shut on their extended tentacles, although they found another path through. Their expedition into the outside world enabled them to take over Wolverine. Attempts to enslave Namor and Namorita were less successful, and Wolvie himself eventually broke free of their control.
People Who Think They're Not So Bad: Iron Fist himself has a certain sympathy for the H'yulthri, although less so after he discovered they were responsible for the death of his sister, Miranda. They formed a successful partnership with the Plant Man, who always preferred plants to people, but disposed of him once they were satisfied that they had established a safe beach-head on Earth.
Most Despicable Act: The H'yulthri are just one of a number of species caught up in the blood-letting machinations of Master Khan, who needs death in order to extend his own life. That being said, they are hardly a passive lot. As the people of K'un Lun have come close to wiping them out generation after generation, the H'yulthri have retaliated with atrocities of their own, and have come close to destroying all the human habitants of that strange dimension time after time. So continues the hideous cycle...