Dang, that dungeon is perfect for training rookie adventurers. It's a shame that it will be destroyed. I don't know why, but I feel that the destroyer will take interest in Lily. BTW, it was fun seeing Lily acting like a chuuni.
More than once, Lily demonstrates the problem with children doing on adventures - without a chaperone at least. Its fun to watch Hajime gradually accepting his new role as a dad.
Rereading the manga, I wonder if our dungeon destroyer is the girl mentioned in chapter 2, page 5, who turns everything to stone. Her closed eyes might hint at a "stone gaze" type ability and her name (Sekihime) might be something like "stone princess" (石姫, although the raws use katakana).
What is this? I had a 'proud dad' flash after the girls beat the scarecrow knight, lol. Good to see them progress a little towards becoming full-fledged adventurers.
It'd be useful if one like that appeared someone more convenient, but the journey to it was more dangerous than the dungeon. Nobody wants to go through level 20-30 game content to fight the level 1 dungeon.