The cast really starts to gel in this volume, focusing mostly on the expedition squad. Bell Cranel's front and center, obviously, grappling with the weight of being a leader after his level up. Welf Crozzo gets some fantastic moments too; his magic swords become crucial, and we see his internal conflict about using his family's craft. Mikoto Yamato's spiritual sensing abilities are highlighted as the group navigates the confusing floors.
Lilly's support role is as vital as ever, but she's more in the background here. The real standout introduction for me was Asfi Al Andromeda. She's the captain of the 'Paras' familia and shows up with this cool, pragmatic air, offering the 'Grimoire' item that becomes a major plot point. Her dynamic with Bell is interesting—less personal, more of a businesslike alliance. Oh, and the Juggernaut, though not a 'character' in the traditional sense, is absolutely a key presence introduced; it's this relentless monster that forces everyone to their absolute limits.
Volume 9 spends less time on the home-base characters like Hestia or Ais and really hones in on the dungeon-crawling team and their new, enigmatic ally.