Ringworld

Human spacefarer leading the Ringworld mission; ex-wirehead who destroys the sunflowers, deduces the Pak origin of the Ringworld, and infiltrates the floating city disguised as a shadow farmer.

Kzin warrior; co-deduces the Pak origin theory with Louis, enforces secrecy from the Hindmost, and saves Louis from the silver-haired woman in the tower.

Pierson's puppeteer orchestrating the mission for political reinstatement; controls Louis via droud remote and Chmeee via boosterspice; deposed former Fleet leader with hidden knowledge of the Ringworld bacterium.

City Builder woman and Louis's former lover from the first Ringworld expedition; stolen from the ARM by the Hindmost to serve as guide; her disappearance catalyzed Louis's wireheading.

Predecessor puppeteer whose tasp use on Louis triggered his eventual addiction; mated with the Hindmost; referenced as backstory throughout.

Ruler of the grass giants; submitted to Louis's God Gambit, retrieved the boulder for the repulser plate weapon, and witnessed the sunflower destruction.

Young Ringworld native; serves as guide to River's Return and the floating city, learns the truth of the Ringworld's instability, and helps Louis infiltrate the shadow farm.

Unnamed pale woman from the tower battle site who seizes Louis in rishathra frenzy and bites his throat before Chmeee intervenes.

Pak protector who crossed thirty thousand light-years to rescue the lost Earth colony; died learning the breeders had mutated beyond recognition—referenced in exposition.

Belter miner who ate tree-of-life and became a protector; provided the UN with the Pak backstory before disappearing—referenced in exposition.

Lyar Building's master; explains city politics to Louis and accompanies him to Orlry Building, shielding him from extortion.

Master of Orlry Building; attempts to detain Louis by force to seize the superconductor cloth and laser weapon.

City Builder librarian, white-haired and young; assists Louis's research then is involuntarily brought aboard Needle; shares traumatic history of rishathra obligations.

Young City Builder male; emotionally devastated upon learning his people and all those he knows are among those who must die.

Former human companion turned Pak-style protector; traps the crew but covertly guides them toward the solution she cannot execute herself, hoping to lose the fight.

Teela's companion who also underwent protector transformation but died from tree-of-life hunger after a thousand years; backstory figure only in these snippets.