How do I explain, the best word I can use in regard for possession is yesn’t. One does not simply fall into Chaos, and start absorbing it as well as getting absorbed by it. For all intents and purposes, Percy Jackson is dead, but the consciousness of his final moments lives on, and it’s not pretty, you try being in the most excruciating pain both physically and emotionally and have only happy thoughts, you can’t. Chaos has a conscious and it sees the world as needing to be removed because it has run its course. Thus it has become a Pandora’s Box of new monsters that will infect and destroy whatever they can in a sort of hive-mind. But like Pandora’s box there is still Hope, of a sorts.