In many stories like this, there could be a local guide who is familiar with the area around the lost caverns of Ixalan. There might also be a character with special abilities, like the power to communicate with the creatures in the caverns. And perhaps a scientist - type character who is interested in studying the unique geology or magic of the caverns.
There could be a fearless leader type of character who guides the group through the lost caverns. Maybe also a wise old mentor figure who has some knowledge about the caverns. And of course, there might be antagonists, like those who want to use the power of the caverns for evil or greedy purposes.
I'm not entirely sure as I haven't read it in full. But generally, it might involve adventures in the caverns of Ixalan, perhaps with characters exploring the unknown, facing challenges and discovering secrets within those lost caverns.
Typically, the main characters would be the lost children, of course. And there could be other supporting characters like a wise old man who gives them advice, or a mean villain who tries to stop them from getting back home. There may also be some animals that befriend the children and help them on their journey.
It depends on the specific 'lost boys story'. In some cases, the main characters could be a group of orphan boys. In other versions, it might be boys who have run away from home.
In some 'lost city stories', the main characters could be a group of scientists. They are interested in studying the history and culture of the lost city. They use their scientific knowledge and tools to uncover the mysteries of the lost city, such as analyzing ancient texts, excavating ruins, and decoding symbols found in the city.
If it's a more complex story, there could be characters from the girls' past that play important roles. For example, a memory of a family member could be a driving force for one of the girls. Or perhaps there is a mysterious figure that the girls keep encountering during their lost journey, and this figure's identity and motives are slowly revealed as the story progresses.
I don't know the story well, but it's likely that the two friends are the main characters. One would be the 'lost' friend and the other would be the one who is experiencing the loss or trying to find the lost friend.
In a typical 'a lost boys story', there would be the group of boys who are lost. There may be a boy who is the thinker of the group, always coming up with plans to escape or find help. Another character could be the joker, who tries to keep the morale high in the difficult situation. And of course, there could be an antagonist, someone or something that is causing them to be lost or preventing them from getting out of the situation.
Since I don't know the exact 'lost in the stars story', I can't say for sure. But it could be an astronaut, a stargazer, or some sort of space traveler.
In the 'the lost city story', the main characters could be a diverse group. There might be a lead archaeologist who has dedicated their life to finding lost civilizations. Alongside them, there could be a team of assistants, each with their own skills, like a geologist to study the land around the lost city, and a historian to piece together the story of the city from old records. There could also be native inhabitants of the area where the lost city is rumored to be. Some might be helpful, guiding the outsiders to the location, while others might be wary, fearing that the discovery will disrupt their way of life.
Since we don't have much information, it's difficult to say for sure. But it could be the lost stars themselves.