There may be some court officials or servants who play significant roles. They could be spies, allies, or informants for the empresses. Their actions can either help or hinder the empresses' plans in the complex web of palace politics.
The emperor would be an important character as well. His decisions, preferences, and power directly impact the lives and fates of the empresses. For example, if he favors one empress over others, it can cause jealousy and power shifts among them.
Well, surely the empresses themselves are notable characters. Each empress would have her own personality, goals, and backstories that shape her actions in the palace.
Love and betrayal might also be important. There could be complex relationships between the empresses and the emperor, as well as among the empresses themselves. For example, they might pretend to be friends but secretly plot against each other. And the love they have for the emperor or others can lead to various betrayals when interests collide.
Koko Hekmatyar is a very notable character. She is a young and brilliant arms dealer. She has a charming yet dangerous personality. She's able to navigate the complex world of arms trading with ease and is highly intelligent, always one step ahead of her opponents.
Then there's Alexis Douse, who is part of the ruling class and his actions and motives are crucial in understanding the political side of the Grancrest War. His character is complex as he has to balance his personal ambitions with the needs of his faction in the context of the ongoing war.
The archmage himself is obviously a very notable character. He's likely the central figure around which the story revolves. There may also be a mentor figure, someone who guides the archmage in his early days of learning magic.
The protagonist is of course a notable character. His journey and development are central to the story. There may also be a mentor - like figure who helps him understand the isekai world better.
There could also be an antagonist or a group of antagonists. They would be the ones creating obstacles for the main character and other protagonists. Their actions and motives would be crucial to the development of the mystery and the story as a whole. They might be trying to prevent the riddle from being solved for their own gain or to maintain some sort of power or control within the world of the light novel.
Well, Nero Claudius is a very important character. She is a Servant with a regal and powerful presence. Her relationship with Hakuno Kishinami is an interesting aspect of the story. Then there's Tamamo no Mae, another Servant. She has a charming and somewhat devious personality. These characters, among others, contribute to the rich tapestry of the Fate Extra Light Novel.
Ainz is the most notable character. He is the powerful overlord who is trying to make his mark in the new world. His decisions drive the overall plot. Then there are the floor guardians in Nazarick like Albedo, who is extremely loyal to Ainz and often has her own ideas about how to serve him better.
Ayato Amagiri is a very notable character. He has strong combat abilities and is a key figure in the story's battles.
One significance is that it showcases the power dynamics in the imperial court. The empresses' battles for influence were intense. Another is that it gives a view of the fashion and aesthetics of that time. The elaborate costumes described in the fiction are a part of it.