The Storm God's Descendant is absent, but there's still a bit of the Flame Divine Successor left. Let's make do with that. The World-devouring Slime only appears in legends, and no one has seen it in reality. It's better for everyone to give up trying to extract casting materials from it... To help Tassera gather casting materials, even Leon, going at it personally, spent several months.
When Tassera prepared the Tassela Ascension Technique, Leon was definitely going to watch. He saw the Blue Dragon set up a gigantic array large enough to contain her true form... The casting itself lasted half a day, and nothing seemed to happen in the end.
"Is it done?"
Cecilia loved to join in the fun, and she was certainly among the spectators at this moment, poking her head around.
