Since I haven't delved into 'the Winter King' novel, it's difficult to name the exact main characters. However, based on typical fantasy or historical fiction themes, apart from the eponymous Winter King, there could be a brave knight who is loyal to the king. There might also be a wise old wizard or a cunning court jester who, in his own way, influences the events in the kingdom. And of course, there could be an enemy leader who is constantly plotting against the Winter King.
Not having read the 'Winter King' novel makes it tough to accurately list the main characters. But if we think about common elements in such stories, the king is likely at the center. He may have a trusted general by his side, someone who is excellent in warfare and strategy. There could be a female character, maybe a healer or a prophetess, who has a special connection to the forces of nature, especially winter - related ones. And there would probably be some power - hungry nobles within the king's court who create internal conflicts for the king to deal with.
Since I haven't read it, I can't say for sure. But likely, the king himself is a main character. There might also be his queen or love interest, some important knights or generals in his army, and maybe a villain who is causing trouble in the kingdom.
In the 'king winter story', King Winter is probably the main character. However, depending on the nature of the story, there could be other important characters. For example, if it's a story about a journey, there might be a group of companions who accompany King Winter. These could be a wise old man who has knowledge of the winter magic, a young boy who is eager to learn from the king, and a talking animal, like a wolf or a raven, which could be his guide or messenger.
In the 'king winter waldorf story', the obvious main character seems to be King Winter. He is the central figure around which the story might revolve. Then, there could be characters such as his councilors in Waldorf, who help him make decisions for the kingdom. There may also be a character who is a rebel or an outcast, challenging King Winter's rule. Additionally, there could be characters representing the different aspects of Waldorf, like the forest keeper who is in charge of the woods in Waldorf and has a relationship with King Winter, either as an ally or an adversary depending on how the story unfolds.
Arya Stark is also a common character paired with the Winter King in fanfiction. Arya's skills as an assassin could be useful to the Winter King's cause. She might be sent on secret missions by him or they could form a bond over protecting the innocent in the North.
There might be a female character who is either a commoner with a special gift or a noble from another land. She would be the love interest of the king. There could also be side characters like loyal knights or cunning advisers who play important roles in the story, either helping or hindering the relationship between the main characters.
The winter king would be a key character for sure. There might also be characters like his loyal subjects who depend on him during the winter. And perhaps there are some opposing forces, like those who try to disrupt his rule or the natural order of winter.
The Winter King himself is surely a main character. There might also be his loyal subjects, perhaps some knights or advisers who help him rule his wintry kingdom.
The main characters might include a detective if it's a mystery set in winter. He or she could be a jaded but brilliant investigator who has to deal with the cold and the secrets that the winter seems to hide. There could also be a group of friends who find themselves in a dangerous situation during winter, like being trapped in a remote cabin with a murderer on the loose.
In 'the winter soldier novel', the most prominent character is the Winter Soldier. However, other important characters may include those who are trying to help him break free from Hydra's control. There could be some fellow soldiers or agents who discover his true nature and decide to assist him. Also, antagonists within Hydra who will do anything to keep him under their control are likely to be part of the main characters in the story.
Since I'm not familiar with 'the winter girl novel', it's difficult to name the main characters precisely. But based on the title, the central character is the winter girl. She may have a best friend who stands by her side throughout the events of the story. There could also be an older person, perhaps a grandparent or an old family friend, who imparts wisdom to her during the winter. Additionally, there might be a character who is a bit of an outcast in the story, and the winter girl forms an unexpected bond with this person, which becomes a crucial part of the plot.