In Agatha Christie's 'And Then There Were None', ten individuals are lured to a secluded island under false pretenses, setting the stage for a series of mysterious deaths.

Dr. John Watson is Sherlock Holmes' loyal friend and chronicler, often accompanying him on his detective adventures and providing a rational perspective.

The Priory of Sion is a fictional secret society featured in 'The Da Vinci Code', believed to be the guardians of a hidden truth about the lineage of Jesus Christ.

Bess Marvin is Nancy Drew's closest friend and often joins her on her detective adventures, providing support and assistance.

Hercule Poirot is the renowned Belgian detective featured in many of Agatha Christie's mysteries, known for his meticulous attention to detail and brilliant deductions.

The Hardy Boys operate their own detective agency, named the 'Hardy Boys Detective Agency', where they solve mysteries and uncover secrets.

The LEP (Lower Elements Police) is a secret organization in the 'Artemis Fowl' series, responsible for maintaining peace and order in the fairy world.

Encyclopedia Brown's loyal dog, Sally, often assists him in solving mysteries and uncovering clues.

The Vespers is a secret society in the '39 Clues' series, believed to possess ancient knowledge and artifacts of great power.

The Magic Tree in the 'Magic Tree House' series allows Jack and Annie to travel through time and embark on exciting adventures.

The Nereids in the 'Percy Jackson' series are water nymphs with shapeshifting abilities and control over water.

Aslan is the majestic talking lion in the 'Chronicles of Narnia' series, who represents goodness, wisdom, and the true ruler of Narnia.

The Magisterium in the 'His Dark Materials' series is a powerful organization that seeks to maintain control over all worlds and suppress knowledge.

The Time-Turner in the 'Harry Potter' series is a magical device that allows wizards to travel back in time, though its use is strictly regulated.

The Mysterious Island in the 'Mysterious Benedict Society' series is a secluded location where children are recruited and trained for covert missions.