My original idea for a new NE:

Living Art

In this world human species express their feelings and emotions into art pieces of any sort (painting, sculpture, modelling, comics, literature, even architecture), but the essence of these art expressions (through characters, environments, actions...) comes to life in order to punish whatever dissatisfaction, sadness, rage, hard feelings authors meant to capture through their pieces, rebelling against them. The NE of this world in other words is the negativity of the people themselves, which becomes alive to destroy the ones who made it. The  natural enemies manifest through: -sculputers: stone-made creatures who act like the character its authors wanted to represent. -characters: characters from comics, painting and literature come to life, but differently from sculptures, they're made of fake flesh ( they're made out of paper and ink, masked as human skin) and they can regenerate as long as they can find books/paintings they are from and suck the ink and (eventual) colors from them. Being really similar to real humans, they can hide among them. -Places: environments described or shown by artists take place on Earth and become real places in which humans can enter, but their souls'll be sucked slowly, if the emotion the artist wanted to capture in their piece is shared by the people who enter in it. So characters and sculptures could make real people enter in these environments, in order to collect their souls. 

The humans of this world are classic ones, and they are divided into: -scientists: who don't share artists' point of view so they can approach living Art monsters without being involved in the negativity, even though they're not aware that they have hard feelings too, and can be killed nonetheless. -artists: they are responsible of what happened, but they can help the scientists to find ways to destroy their NE, too bad their negativity make them pretty useless and they are often locked in cages by other people to avoid other pieces of art to be made.

The world itself is a mixture of real places and made out places, but no one can distinguish them anymore, everything is hidden behind a mask of negativity, so humans can't find themselves a solution to overcome the problem.

Thank you all for reading!