There's the lone survivor who is often the main focus. This character has to use their wits to stay alive in the unforgiving environment.
Since we don't have much information about 'the long dark story', it's hard to say for sure. However, it might have a protagonist who is a strong - willed individual, like a hunter or an explorer. There could also be supporting characters such as a wise old man who gives advice, or a young sidekick who is learning the ropes of survival in this long dark situation.
I'm not familiar with this specific story, but typically in a story about a long, dark situation like this, there might be a protagonist who is the central figure going through the challenges. There could also be an antagonist, perhaps in the form of the harsh environment or other people who are causing trouble for the main character. And there may be some side characters like a friend or a mentor who offer support or guidance at certain points.
Since I haven't read the 'long dark water story', I can only guess. There could be a protagonist who is on a quest related to the long dark water. It might also have a wise old character who imparts knowledge about the water's secrets. There could be a sidekick character as well to accompany the main character on their journey.
Since I don't have much information about this story, I can't say for sure who the main characters are.
Obviously, the Dark Magician is one of the main characters. It's the central figure in these duel stories.
An adventurer might be a main character. They are used to facing challenges and the dark room is just another mystery for them to solve. They might bring their tools and knowledge to deal with whatever is in the room.
In Dark Duelist Stories, it's possible that one of the main characters is a duelist who has a special connection to his cards. He might be able to draw out more power from them compared to others. Another could be a duelist who was once defeated but comes back stronger and more determined than ever to make a name for himself in the dueling community.
There might also be an antagonist who represents the 'dark' side more directly. This character could be trying to corrupt the protagonist or disrupt the balance in the story's world. They could have their own motives, which may be related to power, revenge, or some other dark desires.
In some 'Dark Night Stories', the main character could be a young detective trying to solve a mystery that occurs during the night.
I'm not sure exactly, but there could be brave adventurers.