This story takes place before Rimuru's reincarnation. Shizu, also known as the Conqueror of Flames, responds to an urgent request calling her to the Kingdom of Filtwood. When she reaches the castle, many adventurers are already there. What request could have demanded such a huge gathering? It turns out a demon has been revived, and the adventurers have been called to subjugate it. It is said that more than ten of the most skilled adventurers have already been killed by this demon. But there is more to this request than meets the eye...
of demons who were known as the progenitors.
عن شياطين كانوا يُعرَفون بالأسلاف
dass es die sogenannten ersten Dämonen gab.
de los entes demoníacos
conocidos como progenitores.
de los entes demoníacos
conocidos como progenitores.
qu’il y avait des démons
dits primordiaux.
Gli chiesi dei diavoli 
che venivano definiti i progenitori.
sobre demônios conhecidos
como progenitores.
На свете есть демоны-прародители…