Invader

Hearing a new term had once again sparked Lin Mu's curiosity as he wondered what it meant. Lin Mu waited patiently for senior Xukong to explain it to him.

"In a simplified manner, an invader is basically a being that enters a world that it's not allowed to. It does so to gain control of that world or to obtain its resources. 

You see, most worlds have an innate barrier present in them. There are created and operated by that world's will." Xukong spoke.

"World's will? Senior, you mean each world is alive?" Lin Mu questioned while tilting his head.

"Not exactly. While it may or may not have had life on its surface, every world can have a certain level of sentience. Not all worlds have it, though. Some worlds are simply too young to have developed it, while others lose it due to dying or being destroyed."