Celaena is a sixteen-year-old orphan raised by the Assassins' Guild master in Rifthold. She holds the title of Adarlan's Assassin, possessing lethal combat skills and a reputation for unmatched deadliness. Despite her profession, she maintains a strict personal morality regarding innocent lives and refuses to target people she deems undeserving. She loves fine clothes, expensive perfumes, and classical music, quietly harboring a desire for a peaceful life outside the guild.

Sam is a highly skilled teenage assassin operating out of the Rifthold guild. The son of a murdered courtesan, he was taken in by the guild master to avoid a life on the streets. He views himself in direct competition with his peers, though his antagonistic exterior hides deep loyalty. He refuses to hurt innocent people and saves his money in hopes of eventually leaving the dangerous lifestyle behind.

Arobynn is the self-titled King of Assassins who runs the deadly guild in Rifthold. He recruits young orphans and shapes them into lethal killers through brutal physical and emotional conditioning. He maintains vast wealth and influence across the continent, viewing his assassins as personal property. He demands absolute obedience and uses psychological manipulation to pit his students against one another.

Ansel is a teenage assassin training with the Silent Assassins in the Red Desert. She wears distinct armor adorned with wolves and rides rare Asterion horses. She fled her home in the Flatlands after a neighboring lord murdered her family, turning to a life of violence for survival. She desires vengeance above all else and plots to reclaim her stolen homeland by any means necessary.

Yrene is a young woman working as a barmaid in the rundown port city of Innish. Originating from Fenharrow, she possesses latent healing abilities passed down from her mother, who was murdered by Adarlanian soldiers. She saves her meager earnings with the hope of traveling to the southern continent to formally study medicine at the Torre Cesme. She is earnest, hardworking, and vulnerable to the dangers of the port city.

Lysandra is a teenage courtesan living in Rifthold under the strict mentorship of her madam. She prepares for her Bidding, a high-society auction that will mark her formal entry into sex work. She uses her beauty and charm to manipulate wealthy patrons and secure her place in the city's hierarchy. She frequently clashes with the female assassins who operate in her social circles.

Rolfe is the Lord of the Pirates, operating out of Skull's Bay in the Dead Islands. He maintains his power through ruthless violence, having murdered his competitors to secure his title. He bears magical tattoos on his hands that function as a map, though the magic itself has faded since the king's ban. He engages in illegal trade agreements to enrich his sprawling pirate fleet.

The Mute Master is the silent leader of the sessiz suikast, or Silent Assassins, located in an oasis fortress in the Red Desert. He trains his disciples in fluid, nature-inspired combat techniques modeled after desert wildlife. He observes his students closely before deciding whether to take them on for personal instruction, rewarding patience and moral character.

Farran is the sadistic second-in-command to a prominent crime lord in Rifthold. He orchestrates brutal pit fights in the city's criminal underbelly. He tortures his victims for pleasure and seeks to expand his influence over the illicit networks of the capital, employing poisons and traps to secure his power.

Jayne is a powerful crime lord operating in the shadowy underbelly of Rifthold. He commands a large network of guards and controls much of the city's illicit activities, maintaining enough power that even the King of Assassins hesitates to cross him openly.

Doneval is a prominent businessman from the nation of Melisande. He travels to Rifthold under the guise of negotiating a road construction deal with the Adarlanian government. He holds secret meetings in his heavily guarded estate to manage sensitive political documents.

Ilias is the handsome son of the Mute Master. He lives in the Red Desert oasis, where he trains alongside the other assassins in the fortress. He participates in the physical defense of their territory against local warlords and shows an immediate romantic interest in visiting assassins.

Mikhail is an older, senior member of the Silent Assassins in the Red Desert. He has not taken the vow of silence and speaks freely. He assists in training new recruits and defending the fortress from outside attacks, while maintaining a long-term relationship with one of the younger students.

Berick is the ruler of the desert city of Xandria. He commands a large military force and frequently launches raids against the nearby assassin fortress in hopes of claiming their territory to curry favor with the Adarlanian empire. He hoards rare Asterion horses in his stables.

Bardingdale is a wealthy businesswoman who travels to Rifthold. She involves herself in high-stakes political maneuvering and hires the Assassins' Guild for a sensitive contract involving stolen documents, pushing her own agenda regarding continental trade.

Dia is an enslaved man held captive on one of Captain Rolfe's ships in Skull's Bay. Because he speaks the common tongue, he acts as a point of contact and translator for the other captives held in the ship's brutal conditions, holding onto the hope of survival.