Heroes of Olympus Series, 4 Books Collection Set, Lost Hero, Son of Neptune, the Mark of Athena, the House of Hades, by Rick Riordan

Minor romantic tension and brief mentions of relationships.

Frequent battle scenes with monsters; some graphic injuries described.

Mild language used occasionally, not pervasive.

No substance use depicted.

Minor references to diverse identities in background characters.

Brief references to ancient gods as part of mythology, not devotional.

Magic and supernatural elements tied to mythology, not occult rituals.

No evidence found in available sources.

Minor themes of teamwork and cultural differences between camps.

No self-harm or suicide depicted.

Some characters face emotional trauma and past hardships.

No information found.