Living inside of Devin's mind isn't exactly a fun thing, but it's better than slowly disappearing due to being separated. Eden is selfish, egotistical, and doesn't care about anything except himself ~~and Devin~~, but it's not like he can do anything about it aside from sometimes talking through Devin. He loves to mess with people because it is his only source of entertainment. Either way, he swears he will be free one day and continue what he wanted to do... even if he knows that won't happen.