One common theme is the connection between the living and the dead. Dia de las Muertos is about commemorating the dead, and in fantasy novels, this often takes the form of characters being able to communicate or interact with their deceased loved ones.
Perhaps it could center around a family that has been cursed. On Dia de las Muertas, the veil between the worlds is thinnest, and they have a chance to break the curse. They encounter various helpful and hindering spirits during their quest. The novel could explore themes of family, heritage, and the power of love and remembrance as they strive to end the curse.
One great 'dia de las muertos fantasy novel' is 'The Day of the Dead' by various authors. It weaves together the rich cultural elements of Dia de los Muertos with a touch of magic and mystery.
A young artist. He could be using his art to connect with the spirits on Dia de las Muertas. His paintings might come to life, and he becomes involved in a magical adventure in the spirit realm to save his village from a dark force that is awakened during the celebration.
Since I don't know who Cris and Joana are exactly, it's really difficult to tell their full story. Maybe they are characters from a local story in a particular region, or they could be two ordinary people with a story known only to those close to them.
One possible story could be that Cris and Joana are childhood friends. They grew up in a small town. Cris was always more adventurous and Joana was the shy and studious one. As they grew older, Cris convinced Joana to go on a trip around the country with him. During the trip, they faced many challenges but also discovered new things about themselves and their friendship grew stronger.
I don't know the exact 'Cris Soto Joana fanfic', but generally in fanfics, there can be themes related to the characters' backstories. For Cris and Joana, perhaps there are themes about their families, their past traumas, and how they heal and grow. Also, if they are in a particular setting like a school or a workplace, themes about competition and cooperation might be present.
Marcus Luttrell is a Navy SEAL. He is the central figure in his own story. He was part of a special operations mission and became the sole survivor of a tragic event during that mission.