Isn't he being a bit of a hypocrite? After all, he did almost devour the core of the Demon World which I'm pretty sure would've destroyed it. He only stopped because he was told that he couldn't succeed in the middle of trying.
I'm curious if he is planning on subduing the planet core while the grandmaster is watching. Perhaps he could use a blood world after penetrating to the core? Or is that possibly part of the plan to scare others with his ability to take over the planet?