The process is so taxing that Rimuru falls into a "sleep mode" for three days to recover his energy.
You can catch this episode and the rest of the series on Crunchyroll or Funimation . Tensei shitara Slime Datta Ken (Dub) Episode 3
When he wakes up, the creatures have evolved. The frail village elder becomes the buff Rigurd , and the Goblins transform into larger, more capable Hobgoblins . New Rules for a New Society The process is so taxing that Rimuru falls