It could also be a new character created specifically for this fanfiction. Maybe a character who has a special connection to Ruby, like a long - lost relative or a mentor figure who has a past related to the rose and thorn concept. This character could play a significant role in the story, guiding Ruby or causing her trouble depending on their motives.
Most likely Ruby. Since 'rose' is in the title and Ruby is often associated with roses in RWBY. The 'thorn' part could be something or someone that challenges her, like a new enemy or an internal struggle she has to face.
In RWBY fanfiction, Commander Thorn could be a character created by the fanfic writer. He might be a military - type figure, perhaps in charge of a group within the RWBY universe's fictional military structure. He could be involved in battles, strategic planning, and leading troops against the various threats like Grimm or other antagonistic forces.
One interesting aspect could be the unique character interpretations. In fanfictions, authors often explore different sides of the RWBY characters, like Ruby's growth in new and unexpected ways. Maybe the 'rose thorn' part implies a certain theme related to Ruby, perhaps a more complex or darker side of her journey that the original series might not have fully delved into.
Another possibility is a new character introduced specifically for this fanfic. This character could be an outsider to the RWBY world, coming from the world of the crossover. They find the single rose and have to navigate the RWBY universe while dealing with the power the rose gives them. It could be a really interesting way to explore both universes from an outsider's perspective.
It could also be a side character like Penny. If she gets damaged in a battle and is taken to the hospital for repairs. The story could focus on how the RWBY team reacts to her situation, and Penny's own thoughts as she is being fixed. Also, it could explore the relationship between Penny and the people in the hospital who are helping her.
A grizzled veteran mercenary who has seen many battles and has a lot of combat experience. He could be cynical at first but slowly warm up to the RWBY team.
Ruby could be the main character. Since she is the protagonist in RWBY, it would be natural for her to be the one to find the ring. She could be intrigued by its power and try to figure out how to use it for good in the fight against Salem.
A talented artist could be the main character. In a world that values only practical and money - making skills (the thorns), this artist, with their creative and free - spirited nature (the rose), struggles to find their place but also manages to inspire those around them to see the value of art and beauty.
Since we don't have more information about this fanfiction, it's difficult to determine the main character. However, if the theme of 'a thorn in my side' is related to something like guilt or a difficult decision, it might be a character like Asriel. He has a complex backstory with a lot of emotional baggage that could be considered a 'thorn in his side'. But again, this is just speculation.
It could be the main RWBY characters like Ruby Rose herself. Since it has 'Blood Rose' in the title, Ruby might be central to the story.
The main characters in RWBY Black Rose fanfiction are Ruby Rose and Blake Belladonna. Ruby is a young and powerful huntress with a positive attitude and great leadership skills. Blake is a former member of the White Fang, intelligent and skilled in combat.