Since I don't know the specific 'death watch novel', I can't say for sure. But they could be the people on the death watch, like a doctor, a family member, or a professional caregiver.
Since it's a Kirby - centered fanfiction, Kirby is most likely one of the main characters. There could also be other characters from the Kirby games that Kirby might be fighting against or teaming up with in this death battle scenario.
I don't know the specific 'City of Death Novel' you're referring to, so I can't say for sure. But it could have a brave hero who is trying to save the city from whatever is causing all the death.
I'm not sure specifically as I haven't read the novel, but likely there would be a detective or an investigator type of character who is trying to solve the mystery of the death.
I'm not sure without reading the book, but often in a novel set in Death Valley, there could be a rugged explorer as a main character.
The main characters are likely the Death Troopers themselves. They play a central role as the novel is named after them.
Since I haven't read the 'ambassadors of death novel', I can't say for sure who the main characters are.
Since it's called 'Untimely Death A Novel', the main character might be the one whose death is untimely. There could also be those around this person, such as the people who are most affected by the death. Maybe a lover who is left behind and has to deal with the pain and confusion. Or a sibling who starts to question the events leading up to the death and tries to find out the truth. It's also possible that there is a character like a doctor or a coroner who has some role in the events following the death.
Since I don't know the 'death tropper novel' well, I can't say for sure. But it might have a fearless leader among the death troopers as a main character.
I'm not entirely sure about all the main characters in the 'death stranding novel' since I haven't read it fully. But based on the game, in addition to Sam, characters like Mama, who has a special connection to a BT, could be important in the novel. There may also be new characters introduced in the novel that play crucial roles in the story, perhaps some leaders of the different settlements or people who have special abilities related to the chiral network.
A commoner or a peasant could be a main character too. This character would represent the ordinary people who were most affected by the Black Death, showing their struggle to survive, their losses, and how they coped with the horror of the epidemic.