I'm not entirely sure about all the new characters in volume 14. But sometimes new characters are introduced to either help or hinder the main characters' progress. They could be other adventurers, or perhaps some mysterious figures related to the dungeon's secrets.
There might be new characters who are related to the deeper lore of the Danmachi world. For example, characters who have knowledge about the ancient times of the dungeon or the origin of certain magic. These new characters could be the key to unlocking new storylines and developments for Bell and the others.
There might be new adventurers who join Bell's party temporarily or become their rivals. These new characters could bring in new skills and perspectives. Maybe there are also some characters from the background of the dungeon world, like merchants or informants who have important information related to the new challenges in Volume 8.
I'm not entirely sure about brand new characters introduced only in Volume 7. But of course, Bell Cranel remains very important. His growth and development are central to the story. And Hestia, as his goddess, is always significant. Other existing characters like Ais Wallenstein also continue to have an impact on the events in this volume through their interactions with Bell.
Unfortunately, without having read Danmachi Volume 19 Light Novel in full, it's difficult to name the new characters precisely. But typically, new characters in the series are designed to bring fresh challenges and interactions. They could be powerful adventurers that Bell and his friends have to team up with or compete against, or they could be some strange creatures from the deeper parts of the dungeon with their own motives and behaviors.
Bell Cranel is surely one of the important characters as he is the main protagonist. His actions and growth are central to the story.
I don't have the specific information about new characters in Volume 15. But it's possible that there are new characters related to the religious or cultural aspects of the world in the light novel. Maybe there's a new high - ranking priest or a scholar who has knowledge about some long - lost secrets. These new characters would then interact with Ainz and his comrades, creating new storylines and conflicts.
I'm not sure which new characters are introduced in this volume specifically. It could be characters related to the new areas or story arcs that start in this volume.
I'm not entirely sure as I haven't read Volume 8 in detail yet, but there could be some characters related to the new places Rudeus visits. Maybe a new mentor figure for his magic studies.
One important character could be new adversaries that Ainz and his group face. These characters bring new challenges and often have unique abilities or motives. Another might be some minor characters within the native population of the new world that help to flesh out the world - building aspect.
In this volume, the Lizardmen leaders such as Crusch Lulu are important. They represent the native species that Ainz has to deal with. Among Ainz's subordinates, Demiurge also stands out. He is very intelligent and his strategies and ideas are important for Ainz's plans. There are also other minor characters among the lizardmen tribes that add to the richness of the story.
I'm not entirely sure which new characters are introduced specifically in volume 9. But generally, in the Overlord series, characters like Ainz Ooal Gown remain extremely important. His actions and decisions drive most of the story. The floor guardians such as Albedo also continue to be significant as they carry out Ainz's orders and protect Nazarick. There may be some minor characters from the human kingdoms or other races that are introduced to show the different perspectives in the world.