A structural catalogue of non-player character types found across interactive fiction, RPGs, and game narratives. Organized by function rather than genre. Each entry describes what the NPC type does within the system—what role it serves, what behavior it exhibits, what relationship it establishes with the player. Comparable in intent to Propp's morphology of the folktale, but for the dramatis personae of playable worlds.
Classification by observable behavior rather than narrative role. These types are defined by what they do in the world when the player watches them or interacts with them. Two NPCs can serve the same narrative function (both give quests) but exhibit completely different behavioral patterns (one patrols, one stands still). Behavior is the NPC's body language—it communicates before dialogue begins.
The character who moves along a fixed route. Guard walks north wall, turns, walks south wall, turns, repeats. The patrol converts static space into dynamic space—the same corridor is safe at one moment and dangerous at the next, depending on where the patrol is in its cycle. The player must observe, time, and act within gaps. The patrol's path is a clock face: it teaches the player to think about when, not just where. Patrols with irregular timing or random pauses are harder to read and create sustained tension rather than solvable puzzles.
EXAMPLE: The sentry walks from the gate to the tower and back. Every thirty seconds, the courtyard is unwatched for exactly five seconds. THE PLAYER'S CHALLENGE IS TIMING, NOT COMBAT—THE PATROL TURNS A SPACE INTO A RHYTHM
The character who exists to make the world feel inhabited. The farmer hoeing a field. The child chasing a dog. The drunk slumped against a wall. Ambients have no mechanical function—they give no quests, sell nothing, block nothing. Their purpose is atmospheric: they are the difference between a living town and an empty set. The ambient's behavior must be legible at a glance (farming, playing, sleeping) because the player will not stop to investigate. The best ambients contain small surprises for those who do stop—a unique line of dialogue, a hidden item, a micro-story visible only to the attentive.
EXAMPLE: Two women sit on a bench arguing about the price of bread. They say the same four lines on a loop. They cannot be spoken to. THE PLAYER WALKS PAST AND THE MARKET FEELS REAL—THAT IS THE AMBIENT'S ENTIRE JOB
The character whose behavior changes in direct response to player actions. Steal from a shop and the shopkeeper's posture shifts—arms crossed, voice cold. Save the village and the farmers wave when you pass. The reactant is a living scoreboard: their visible state encodes the player's reputation, choices, or progress. Unlike the ambient, the reactant notices the player. Unlike the companion, they don't travel with you—they stay in place and mark how the world has changed because of what you did. Reactants are most effective in clusters: an entire town that shifts its behavior creates a tangible sense of consequence.
EXAMPLE: After you broker peace between two factions, guards who once drew swords now nod as you pass. Children point and whisper your name. THE REACTANT MAKES THE PLAYER'S PAST DECISIONS VISIBLE IN THE PRESENT WORLD
The character who must be guided from one location to another while remaining alive. The escort inverts the normal power dynamic: instead of the player being the vulnerable party navigating dangers, the player becomes the protector of someone weaker. The escort's walking speed, pathfinding intelligence, and survival instincts determine whether the experience is tense or infuriating. A well-designed escort stays close, takes cover when prompted, and moves at the player's pace. A poorly designed one wanders into enemy fire, gets stuck on geometry, and walks slower than the player's slowest speed. The escort's helplessness is the mechanic; the player's patience is the resource being spent.
EXAMPLE: "Stay close to me. When I say run, you run." The merchant nods. You open the door to the bandit-filled road. THE PLAYER MUST NOW FIGHT WHILE MANAGING ANOTHER PERSON'S SURVIVAL—SPLITTING ATTENTION IS THE REAL CHALLENGE
The character who follows the player through the world with hostile intent. The pursuer converts every space into an escape problem. Rooms are no longer places to explore but obstacles to navigate quickly. The pursuer's speed relative to the player determines the emotional register: slower than the player creates dread (it's always coming); same speed creates panic (one wrong turn and it catches you); faster than the player creates desperation (you can only survive by tricks and hiding). The unkillable pursuer—one that cannot be defeated, only evaded—is the purest form, because it removes the player's default verb (fight) and forces them into unfamiliar ones (hide, run, deceive).
EXAMPLE: You hear heavy footsteps two rooms behind you. They are getting closer. Every door you open, every corner you turn—the footsteps follow. THE PURSUER DOESN'T NEED TO BE SEEN TO FUNCTION—SOUND ALONE TRANSFORMS THE SPACE INTO A CHASE
The character who calls out to the player unprompted. "Fresh fish! Best prices!" "Adventurer! Over here!" "Psst—you look like someone who needs information." The barker is a behavioral advertisement: they announce their function before the player asks. In dense environments with many NPCs, the barker solves the discovery problem—the player doesn't need to click every character to find the one who matters. The barker's call is also a prioritization signal: it tells the player "I am relevant right now." Barkers who change their call based on context ("You look wounded—I sell potions") are more useful than those who repeat a fixed line regardless of circumstances.
EXAMPLE: Walking through a crowded market, one voice cuts through: "You there! The one with the sword! I know who sent you." THE BARKER SELF-IDENTIFIES AS PLOT-RELEVANT IN A SEA OF AMBIENTS
The character who reflects the player's own behavior back at them. In games with morality systems or reputation tracking, the mirror NPC verbalizes what the system has recorded. "You've killed twelve people since you arrived in this city." "Everyone you've helped remembers your name." The mirror is a behavioral summary—it compresses a long history of actions into a single confrontation. The mirror is most powerful when it reveals patterns the player didn't consciously notice. A player who thought they were being pragmatic hears: "You always choose the option that benefits you, even when others suffer." The mirror doesn't judge—it describes. The judgment comes from the player.
EXAMPLE: "I've watched you for weeks. You help people, yes—but only the ones who can pay. The beggars, the sick, the lost? You walk past them every time." THE MIRROR FORCES THE PLAYER TO CONFRONT THEIR OWN PATTERN OF CHOICES
Answers to examples are in invisible ink after each entry (highlight to reveal)
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