You could also write a fanfiction where the Lord of Darkness has to team up with his enemies to face a greater threat. This would be a great opportunity to explore his character in a different light, showing that even he can put aside his enmity when the situation demands it.
Maybe the fanfiction could explore the backstory of the Lord of Darkness. How he came to be, his early life, and what led him to become the dark lord. It could involve a tragic event that turned him to the dark side.
Perhaps a plot where Naruto, as the 'Lord of Darkness', has to form an unlikely alliance with his former enemies. He uses his newfound dark powers to protect the village in a different way than before, and this causes a stir among the villagers who are both fearful and in awe of him. It could explore themes of redemption and acceptance of the different.
One idea could be exploring the psychological changes of the characters during those 30 days. For example, how they cope with the lack of light and the isolation it might bring. Another could be creating new relationships or alliances that form specifically because of the 30 - day situation.
One idea could be exploring the backstory of the main character in 'Darkness of Birth'. Maybe they had a difficult childhood that led to their current state. Another idea is to create a different ending for the story, where the characters face different fates. For example, the protagonist could overcome their inner darkness in a more unexpected way.
You could focus on the relationship between the sparkle and a character who is initially afraid of it. For example, a young girl who sees the sparkle in the forest at night. She thinks it's something evil but as she gets closer, she realizes it has a warm and positive energy. Then, she devotes herself to spreading the light of the sparkle throughout her gloomy village.
Perhaps a fanfiction where the tiger of darkness has a human form as well. In this form, it tries to blend into society but still has its primal instincts. The story could be about the internal struggle it faces between its human side and its dark, tiger nature. It could fall in love with a human, and then the conflict would be about whether to reveal its true self or keep it hidden.
One idea could be to cross it with a superhero universe. The Darkness' powers would create an interesting dynamic against heroes like Superman or Batman. For example, the Darkness' ability to manipulate shadows could be a real challenge for heroes who rely on light or technology.
One idea could be exploring the backstory of a minor character in 'into darkness'. For example, a crew member who has a hidden past related to the main antagonist. Another could be a time - travel plot where a character goes back in time to prevent the events that led to the 'darkness' in the story. Maybe also a story about a character who discovers a new power or ability that could change the course of the events in the 'into darkness' universe.
Perhaps a fanfiction about a character who is trapped in a dark and silent dimension. They have to rely on their inner strength and memories to find a way out. This could explore themes of self - discovery and isolation.
One idea could be exploring the backstory of the main character in 'Master of Darkness'. Maybe they had a normal life before becoming the master of darkness, and you could write about the events that led to their transformation. Another idea is to create a new villain who challenges the master of darkness in unexpected ways, adding more conflict to the story.