Well, her family members could be great additions. Her parents, for example, could have influenced her in different ways. Also, her siblings if she has any, might be involved in power struggles or family dramas. Another good character could be her loyal servant or bodyguard, someone who has been with her through thick and thin and has some interesting backstory.
A wise old advisor would be a good character. This person could offer Argella valuable advice on ruling, warfare, and diplomacy. A rival from another kingdom could also be included. This rival could be both an adversary in political and military matters, but also someone with whom Argella might find some common ground or even a begrudging respect. And don't forget about the common folk. A peasant or a local merchant who has an encounter with Argella and changes her perspective on the needs of her people.
One idea could be exploring Argella's early life and her training. Maybe she had a mentor who taught her unique combat skills or diplomatic strategies. Another could be a story where she has to form an alliance with an unlikely group to save her people from a great threat.
You might also consider creating new characters. For instance, a scientist who is a descendant of Victor Frankenstein and is trying to either correct his ancestor's mistakes or continue his work in a more ethical way. Or a journalist who discovers the existence of the monster and decides to expose the story, which would then lead to a whole new set of events and interactions involving all the other characters.
Courtney Whitmore (Stargirl) herself is, of course, essential. But adding characters like Pat Dugan, her step - father, can bring in more family - dynamic elements. He could be a source of wisdom and support for Stargirl in the story.
You could include his sidekick, a witty and agile thief named Lira. She could provide comic relief and also be useful in sneaking around. Another good character would be the wise old wizard, Merlinus. He could offer Arcules advice and knowledge about the magic in the world. And a villain like the shadowy warlord, Zargoth, would be great to create conflict.
The Green Goblin is a classic choice. His maniacal nature and his flying glider make for some exciting action scenes. Mary Jane could also be included. Her relationship with Spider - Man is an important part of the Spider - Man lore. And don't forget about Aunt May. She can add some heartwarming and sometimes comical family - related moments to the fanfic.
Draculaura would be a great character to include. She and Clawdeen could bond over their different yet equally unique monster identities. Also, Frankie Stein would fit in well as she's always up for new adventures and could add an element of chaos. And of course, Clawdeen's family members like her parents or siblings can be included to explore family dynamics.
If we consider a crossover with the Lord of the Rings universe, Aragorn could be a good fit. He's a noble leader and a skilled warrior. His presence could force the Boys to reevaluate their ideas about power and leadership, and he could also be a strong ally against any corrupted power - hungry characters from the Boys' world.
You could have an elderly couple who come in every day for their morning coffee. They've been married for decades and share their love story with the other customers. Then there's the young artist who uses the coffee shop as their studio, sketching the people and the interior. And don't forget the over - enthusiastic coffee blogger who visits the shop to review their drinks and ends up getting involved in the shop's drama. There could also be a street musician who plays outside the coffee shop and sometimes comes in for a free cup of coffee in exchange for a song.
A young and brave squire who dreams of becoming a knight. He could be the protagonist, going through various trials and tribulations within the castle walls, learning the ways of chivalry and loyalty from the knights and other characters.
The Terraria Guide could be a great character to include. He has a lot of knowledge about the Terraria world, so in a crossover, he could be the one trying to figure out the new world they're in. For example, if it's a crossover with Terraria and Hollow Knight, he could study the strange bugs and lore of the Hollow Knight world.