So basically this very powerful entity who wants to stop evolution so a species doesn't get smart enough to cause a mass extinction. He was actually really powerful in the past but he was defeated and that allowed multicellular life to evolve. However he was still strong and caused all the mass extinction events but about 0.5 million years ago he was defeated and now in present day is rather weak. About Wall level, and a person accidentally awakens him and he would before latch on to things to make them evolve slower/not evolve but since he's weaker he is now stuck with that person. (Bad grammar due to being rushed)
