Aurora's life didn't change for the better after she was woken by True Love's Kiss and Giselle didn't arrive in New York City after being pushed down a well. Instead, Phillip died in Aurora's arms while Giselle was transported into a far less-harmonious world than her own. Since she was saved by Phillip, Aurora has been plagued by prophetic Bad Dreams. Giselle, too, suddenly has powers that she didn't prior to her encounter with Narcissa.
By the start of the story, several years have passed and the two women have united on a shared cause, with Mulan in tow. The three set out to the city-state of Agrabah together.
Somnium provides examples of:
- Ambiguous Gender Identity: Mulan's gender is written in a way that's up to the viewer's interpretation. She's either bigender or she has two personas. When her hair is worn up, she's Ping and is referred to with he/him pronouns, but she's also Mulan whenever her hair is down.
- Bi the Way: Aurora and Giselle's first loves were Prince Phillip and Prince Edward respectively. They end up becoming each other's Second Love.
- Crossover: Several films get mentioned but the story predominantly crosses-over Aladdin, Enchanted, Mulan, and Sleeping Beauty.
- Culture Clash: Giselle comes from a land where animals talk and bad things rarely happen. It's a culture shock when she arrives in a more real life world. The idea that winter could be dangerous, even deadly, was foreign to her.
- Crossover Couple: Aurora and Giselle have fallen in love by the start of the fic, but they're in a state of Will They or Won't They? until the final chapters.
- Dead All Along: Aladdin and Jafar have been dead for six years. It's only Jasmine's dark magic that keeps their bodies intact.
- Death by Adaptation:
- Phillip died after kissing Aurora.
- Jasmine's father died prior to the story.
- Aladdin and Jafar are Dead All Along.
- Deliberate Values Dissonance: Agrabah has different rules and laws than the places where Giselle, Aurora, and Mulan come from. Women are expected to be demure and subservient to men.
- Dreaming of Things to Come: Aurora's visions come to her in nightmares.
- Fusion Fic: Somnium is a fusion of The Princess Series with Disney Animated Canon (with a bit of Twisted Princess inspiration). It features Disney characters but takes influence from The Princess Series' story.
- Named by the Adaptation: Snow White's prince goes by his fanon named, Ferdinand.
- Mysterious Past: Unlike Aurora or Giselle, Mulan's backstory is not given in-depth. It presumably started like it did in her film, but something changed. Mulan now has a sword with Mushu's powers and she's left her land, but that's all that's told.
- Patchwork Fic: The story takes some elements from the fairy-tales as well as their Disney adaptations. For example, Aurora's castle fell into a sleep alongside her, which happens in some incarnations of Sleeping Beauty.
- Parental Abandonment: Giselle's mother died when she was very young and her father died when he left for a hunt but never returned.
- Seers: Aurora has the ability to dream of future events.
- Witch with a Capital B: After feeling anger for the first time, "witch", directed at Queen Narissa, is the first swear-like word Giselle ever says.