That Time I Got Reincarnated as a Slime S00 E14 Digression: Diablo's Journal

"Ascend into your true form."

After defeating Clayman at Walpurgis, Rimuru officially became a Demon Lord and a member of Octagram. Meanwhile Diablo awaits Rimuru's return in Tempest, and is anxious to learn about his master's activities as soon as possible. A look back at Walpurgis.