Talk:Satoru Mikami/@comment-45137761-20200516064203/@comment-10330822-20200517035347

You mean the Light Novel? The LN is still ongoing, the WN is the only thing that is finished.

Yeah, once Yuuki sends him into "The Void" Rimuru devours insane amounts of nihilistic energy, which completes his Space-Time Control abilities to allow him to teleport to basically whatever time or time-space he wants, which of course includes alternative dimensions like his previous world. The nihilistic energy also functions to counter-act creation allowing Rimuru to annihilate anything he touches it with. And, with the nihilisity energy he has, he can creates rifts in the Void to gather more of it, and store as much as he wants within the unlimited storage space of his Imaginary Rooms.