Since I'm not familiar with 'the king's palace story', it's hard to say for sure. But typically in a story set in a king's palace, the king would be a central figure. He might be accompanied by his trusted knights or generals. There could also be a female lead, like a princess or a powerful sorceress who has an influence in the palace. And of course, the servants who keep the palace running could also be important characters.
I don't know this story specifically, but it could have the king as a main character. There might also be his queen, princes or princesses, and perhaps important advisors or nobles in the palace.
Since I don't know the exact 'king of the palace story', it's hard to say for sure. But most likely, the king himself is a main character. There could also be his queen, if there is one in the story. And perhaps his advisers, servants, and noblemen who play important roles in the events that take place in the palace.
Since I don't know the exact 'the king's palace story', it could be a story centered around the king in his palace. It may involve his rule, his relationships with his courtiers, and the daily life and politics within the palace. Maybe there are tales of grand feasts, important decisions, and intrigues among the palace inhabitants.
Obviously, the undead king is one of the main characters. He is central to the story as the title suggests.
The obvious main character would be the undead king himself. He is likely to be at the center of the story. There could be other important characters such as his advisers, if he has any. They might be undead as well or some other dark entities. And there may be characters from outside the palace who try to enter the palace of darkness for various reasons, like treasure hunters or adventurers, and they could also be main characters as their actions might drive the plot forward.
Since I haven't read it, I can't say for sure. But likely the king of death is one of the main characters.
Since I don't know the story, I can't be sure. But I guess the main character is Rat King Little King.
The main characters are the king, the two swindlers who pretend to make the special clothes, and the little boy who finally tells the truth. The king is a vain character who is easily fooled. The swindlers are clever tricksters, and the little boy is the one with the honesty and courage to say what he sees.
In any story, there are usually supporting characters. For 'King Lisey's story', there could be peasants who are affected by the king's rule. Maybe there are also foreign ambassadors if the story involves diplomatic relations. The king's servants would also be important characters, as they are close to him and might be privy to secrets or play a role in palace intrigues.
In the king's elephant story, apart from the king and the elephant, there could be an elephant keeper. This person would be responsible for taking care of the elephant, feeding it, and training it. So, the keeper also plays an important role in the story as he is the one who has a direct daily interaction with the elephant.
The king and the goldfish are surely the main characters. The king, being in a position of authority, his character traits like his kindness or cruelty might play a role in the story. The goldfish, being the focus along with the king, might have its own 'character' so to speak. Maybe it's a very curious goldfish or a very timid one. There could also be other minor characters like the fishermen who caught the goldfish originally and presented it to the king, or the queen if she has an opinion on the king's preoccupation with the goldfish.