I have no idea who Wally Purling is in this story. However, if we assume it's a typical Christmas story, Wally Purling could be the protagonist. He could be an ordinary person who has an extraordinary Christmas adventure, or he could be a symbol of the Christmas spirit, spreading joy and kindness during the holiday season. But this is just speculation without knowing the actual story.
Wally and Kuki are likely characters in a particular fictional universe. They could be from a TV show, a video game, or a comic. Without more context, it's hard to say exactly who they are, but they are the focus of the fanfiction, which means fans are interested in exploring their relationship, be it friendship, romance, or some other kind of connection.
The team is devastated. Artemis might go into a deep state of grief and blame herself for not being there to protect him. Robin could become more withdrawn and focused on finding out who or what caused Wally's death. Superboy might struggle with anger, feeling like he should have been stronger to prevent it.
Often, the other members of the Young Justice team are involved. Artemis is frequently included. She might be the one trying to rescue Wally or be involved in the events that led to his being trapped. Robin also shows up a lot. He could be using his detective skills to figure out how to free Wally.
Wally could be developed by showing his growth in character. For example, if he was a bit cocky before, he could return more humble and with a deeper understanding of the world. This change could be a result of his experiences while he was away.
Well, I really like the fanfic 'Wally West: Racing Against Time'. It's a thrilling read as it pits Wally against a new and powerful enemy that can manipulate time, which creates a whole new set of challenges for him. Then there's 'Wally West and the Lost Speed Force'. This one is more of an emotional journey as Wally tries to find his connection to the speed force again. And don't forget 'Wally West's Allies and Adversaries' which gives great insights into the characters he interacts with.
A fanfiction might explore the idea of Wally discovering a rare Pokemon and asking Ruby for help. Ruby, being more experienced, could guide Wally on how to catch the Pokemon without scaring it away. This could lead to an adventure where they explore a new area in the Pokemon world, encounter other trainers, and have to use their combined skills to overcome obstacles in their path.