For 'a child of earth and sky fanfiction', a plot idea could be centered around the character's discovery of an ancient civilization that was closely tied to the earth and sky. They learn the secrets and wisdom of this civilization which gives them new abilities. They then use these abilities to face a natural disaster that threatens to destroy the balance between the earth and sky. Along the way, they form bonds with other characters who also have a connection to the earth and sky, and together they fight to preserve the world as they know it.
One idea could be a crossover of characters from different Arrowverse shows on Earth X. For example, having Barry Allen from 'The Flash' team up with Kara Danvers from 'Supergirl' to fight against the evil regime on Earth X. They could use their super - speed and super - strength respectively to take on the powerful foes there.
Maybe there's a fanfiction where a Sith Lord tries to take over Earth. The Earth's military would be no match for the Sith's powers at first. But then, through some clever thinking and the discovery of a hidden Earth - based energy source similar to the Force, they start to fight back.
One interesting plot could be about a new character in the Naruto universe who has the power to control both heaven and earth elements. They could use this power to try and bring peace between warring clans.
The child could be a bridge between the two opposing sides that Merlin and Morgana represent. The child's innocence and unique perspective could start to change the views of those around them, leading to a possible reconciliation between Merlin's side and Morgana's followers. This would involve a lot of character development for the child as well as for Merlin and Morgana as they see the world through the eyes of their offspring.
One idea could be a story where the child of Ladybug and Chat Noir discovers their parents' secret identities by accident. Maybe they find a hidden Miraculous box in the attic and start to figure out what it means.
One idea could be that their child discovers a hidden magic that neither of their parents were aware of. This magic could be a key to solving an ancient mystery in the wizarding world. Another plot could be the child having to navigate the social difficulties of being the offspring of two former rivals, facing prejudice from some pure - blood families who still hold grudges against Hermione for being a Muggle - born.
One idea could be that Percy's child discovers they have special powers like Percy. For example, they can control water in unique ways. Another could be the child getting into trouble at a new school for demigods and Percy having to step in to help.
A possible plot is that the child is born with a unique power that neither Sasuke nor Sakura have. This power could attract the wrong kind of attention, and the child has to learn to control it while also hiding it from those who would misuse it. The story could also involve the child making friends with kids from different ninja clans and trying to bridge the gaps between the clans, just like their parents did in a way. Also, the child might have to deal with the pressure of being the heir to two very powerful ninja legacies.
Maybe their child gets sent back in time to when Adrien and Marinette were still just friends and classmates. The child then has to figure out a way to get back to their own time without changing the past too much. They might accidentally cause some comical misunderstandings between their parents - to - be in the process.
A plot could involve a human child who has a special ability to communicate with all animals in Zootopia. The child is then recruited by the Zootopia police to help solve a mystery that involves a group of animals that seem to be acting strangely. This could lead to an adventure where the child discovers new aspects of the city and its inhabitants.