These creatures are demons who have possessed the resurrected remains of people who died through great violence. The demons are always knowledgeable and resourceful, and the bodies they possess become supernaturally stronger and more resilient. Every Corpsefiend is driven by an implacable lust to kill. Corpsefiends recognize each other instinctively and always work together when they encounter one another. If many Corpsefiends congregate in one place they will begin to use the resources at their disposal to create great engines and machinery of violence and destruction. It is commonly known that the only reason gunpowder exists is because the Corpsefiends were the first ones to make it.
the Tin Golem
The tin golem is a simple construct from some earlier era. Most have been ravaged by rust and mechanical failures, but those that are still active are observed as behaving in a simplistic manner. The tin golem is often found analyzing a structure, plant, or animal and it always speaks an ancient language. Anybody able to decipher the language hears the tin golem declaring a plethora of facts about the object it is examining. Whether these facts are being recorded somewhere inside the tin golem, or it expects others to listen to what it has to say, is not known. When it is done reciting the facts then it goes about dissecting or destroying the object of it's examination.
There are flying cities from the old world. Nobody knows who built them or why they are still floating in the skies, following courses that must have been plotted by their extinct pilots, but their presence causes many people to seek out ways of catching up to and climbing aboard these ancient relics of a former age. Those who chase after the flying cities are known collectively as City Stalkers. Those who hunt the flying cities with dreams of catching up to them and climbing up to them are spurred on by tales who have succeeded. There is a flying city, Greenspire, which many City Stalkers have managed to climb aboard but few have managed to bring anything of value back from. Those who return from greenspire are often changed into reptilian scavengers. Because City Stalkers are so brutally competitive, successfully getting aboard Greenspire and making your way back down without becoming mutated in the process is often treated as a right of passage. You're not a true Stalker of the ancient metropolii until you've climbed Greenspire.
These City Stalkers once climbed Greenspire and returned alttered and different. They still crave the thrill of hunting down and catching the flying cities, but now they also seek to kill any who would compete with or challenge their claim to a flying city. There is always a danger when running into a Greenstalker that they won't believe you if you claim not to be interested in the flying cities, and there is always a danger that they just want to kill you and eat you anyway.
They're out there, they're smarter then you'd expect, and they're hungry. So hungry!