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 the NPC's position in the game's underlying architecture. These types are defined not by what the NPC says or does visibly, but by the structural role they play in the system's logic—the way they connect, block, reveal, or redirect the flow of play. A character may seem like a friendly innkeeper on the surface while functioning structurally as a lock, a fork, or a timer. The structural type is what the designer sees; the surface type is what the player sees. The gap between them is where craft lives.
The character who exists to be acted upon rather than to act. The prisoner to be rescued. The corpse to be examined. The hostage whose presence changes the rules of a fight. The prop has no agency of their own—they are an object with a face. Their function is to give the player's actions a human target, which changes the emotional register of what would otherwise be a mechanical operation. "Open the locked door" and "free the imprisoned child" are the same puzzle with different stakes. The prop is the difference. Props become problematic when the designer forgets they were once characters—when the rescued princess has no lines, no reaction, no interiority. The best props resist their own objecthood: they speak, they have opinions about being rescued, they complicate the operation.
EXAMPLE: The hostage is tied to a chair in the room with three guards. Any loud action risks their life. They cannot help. THE PROP'S PRESENCE TRANSFORMS A COMBAT ENCOUNTER INTO A STEALTH PUZZLE
The character who blocks progress until a specific condition is met. Structurally identical to a locked door, but wearing a human face. "I won't let you pass until you bring me proof of the king's authority." The lock-NPC's advantage over a literal lock is that it can explain why access is denied and what would change that, embedding the puzzle's clue in the obstacle itself. The lock can also be social: a character who won't share information until trust is earned, or who won't sell rare goods until the player's reputation reaches a threshold. The lock's personality determines which verbs the player considers: a lock that seems corruptible invites bribery; one that seems sympathetic invites persuasion; one that seems weak invites force.
EXAMPLE: "The archive is restricted to members of the Scholar's Guild. Bring me your certificate and I'll let you in." THE LOCK TELLS YOU EXACTLY WHAT KEY YOU NEED—FIND THE GUILD, GET THE CERTIFICATE
The character who is the solution to a lock—not someone who gives you a key, but someone whose presence, knowledge, or ability unlocks progress. "Only a fire mage can open that seal. I am a fire mage." The key-NPC must be found, recruited, persuaded, or transported to the point of use. They are a mobile puzzle piece. The key's structural interest lies in the gap between finding them and deploying them: the fire mage may be willing but far away, or nearby but unwilling, or willing and present but demanding a favor first. Each variation creates a different intermediate quest. The key who doesn't know they're a key—who possesses the needed ability but doesn't realize its relevance—requires the player to make a connection the character cannot.
EXAMPLE: The old woman in the market hums a melody she learned as a child. It happens to be the harmonic sequence that opens the resonance gate. SHE IS THE KEY BUT DOESN'T KNOW IT—THE PLAYER MUST RECOGNIZE THE CONNECTION
The character who forces a branching decision. "You can save the village or chase the villain—there isn't time for both." The fork creates a permanent divergence in the player's path. Unlike a lock (which blocks until a condition is met) or a quest giver (who offers a task), the fork splits reality. After the decision, one version of events becomes true and another becomes impossible. The fork's power is proportional to the irreversibility of the choice and the attractiveness of both options. A fork where one choice is obviously better is not really a fork—it's a test of whether the player is paying attention. The true fork offers two goods, or two evils, or one of each with hidden reversals.
EXAMPLE: Two messengers arrive simultaneously. One says your ally is under siege to the east. The other says the artifact is unguarded to the west. Both are urgent. Choose. THE FORK'S POWER COMES FROM THE FACT THAT BOTH OPTIONS HAVE REAL CONSEQUENCES AND YOU CANNOT HAVE BOTH
The character whose state degrades over time, creating urgency. The poisoned ally who will die in three days. The prisoner whose execution is scheduled for dawn. The informant who will flee the city if you don't reach them by nightfall. The timer-NPC converts open-ended exploration into a race. Their declining condition is a visible countdown: each time the player returns, the poisoned ally is weaker, the prisoner more desperate, the informant more nervous. The timer works because human stakes feel more urgent than abstract ones—"the door closes in ten minutes" is less compelling than "she dies in ten minutes." The cruelest timers give the player enough time to succeed but not enough time to do everything else they wanted to do, forcing prioritization.
EXAMPLE: "The venom is slow but certain. I have perhaps two days. After that—" She doesn't finish the sentence. She doesn't need to. THE TIMER-NPC MAKES EVERY SIDE QUEST THE PLAYER TAKES FEEL LIKE A MORAL DECISION ABOUT PRIORITIES
The character who saw something the player needs to know. The witness possesses information about a past event that the player wasn't present for. Their structural function is bridge across time: they connect the player to events that happened before the game began or outside the player's view. The witness's reliability is the central question. Do they remember accurately? Do they have reason to lie? Were they in a position to see clearly? The unreliable witness—who tells a version of events shaped by bias, fear, or self-interest—creates a detective mechanic: the player must gather multiple witness accounts and triangulate the truth. A single reliable witness is exposition. Multiple conflicting witnesses are a puzzle.
EXAMPLE: "I was there when the tower fell. I saw who opened the gate. But I need to know—why do you want to know?" THE WITNESS HOLDS THE ANSWER BUT THEIR WILLINGNESS TO SHARE IT DEPENDS ON THE PLAYER'S APPROACH
The character who provides information that is systematically distorted. Not a liar (who knows the truth and conceals it) but someone whose version of reality is skewed by delusion, ideology, incomplete knowledge, or a fundamentally different framework for understanding events. The unreliable narrator tells the player things that are true from their perspective but false or misleading in context. The structural function is to create productive doubt: once the player identifies the distortion, every piece of information from that source must be mentally corrected. The unreliable narrator is the inverse of the oracle—where the oracle provides truth in cryptic form, the unreliable narrator provides falsehood in clear form. The player who takes them at face value is misled; the player who understands the distortion gains insight not just about the facts but about the narrator's worldview.
EXAMPLE: "The revolution was a disaster. Thousands died for nothing. The old king was flawed, yes, but he kept order." (The speaker is the king's former advisor.) THE INFORMATION IS ACCURATE IN PARTS BUT THE FRAMING SERVES THE NARRATOR'S INTERESTS—THE PLAYER MUST SEPARATE FACT FROM SPIN
Answers to examples are in invisible ink after each entry (highlight to reveal)
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