Before we start, let's define some constants:

Root directory is where npcs configs are located: {EXILED CONFIG DIRECTORY}/npcs

Nodes directory is where nodes are stored: Root_directory/nodes

Root directory stores NPC's templates, Nodes directory stores talk nodes

All files are in .yml format

First of all, we need to create NPC's template file

There is default_npc.yml in root directory. This file describes default npc, that got summoned when npc_create command is used without arguments

Here it's contents:

---
name: DEFAULT
role: Scientist
health: -1
scale: [1, 1, 1]
inventory: [GunLogicer, KeycardO5]
item_held: GunLogicer
root_node: default_node.yml
god_mode: true
is_exclusive: false
affect_summary: false
process_scp_logic: false
events: []
ai_enabled: false
ai: []

name is NPC's nick

role is NPC's role

health is NPC's health (-1 for default)

scale is x, y and z scale of NPC

inventory is a npc inventory

item_held is an item that npc holds

root_node is file of the root node. Path is relative to node's directory

god_mode - if true, NPC is immortal

is_exclusive - if true, only one player can talk with NPC at a time

affect_summaries - if true, NPC will affect round summaries (For example, round won't end if SCP NPC alive with Class D player)

process_scp_logic - if true, NPC will emulate SCP logic (Reviving as SCP-049, Enraging as SCP-096, Clipping through doors as SCP-106 e.t.c)

events - events, that attached to NPC

ai_enabled - if true NPC will use AI system

ai - AI queue of NPC

You can duplicate this file and edit these parameters as you need

Nodes are essentials of NPC's dialogue system

Let's see what is default_node.yml. It's located inside the nodes directory

---
description: NOPE
reply: HELLO THERE
conditions: []
actions: []
next_nodes: []

decription is short description of player's anwer. That's what player talks to NPC. This is useless for root node.

reply is NPC's reply

conditions is condition's array of this node. We will talk about this later. Currently I'll only say that if at least one condition if false this node will be skipped

action is actions's array of this node. There are many actions, each has it's own arguments,so they are described in separate section

next_nodes is player's replies array. If it's empty NPC will end talk. Each element of this array is node's path, relative to the node's directory. For example if we have next_nodes: [somenode.yml, somenode1.yml] in default_node, player will have something like that in his console:

[NpcName] HELLO THERE
Answers:
[0] SomeNodeDescription
[1] SomeNode1Description

So, it's all. You can also duplicate this file and edit it if you want.

To summon your NPC you can write npc load <your file> in the Remote Admin and got your NPC in game!

To talk with NPC type .talk in your console when NPC is near

To answer you'll need to type .answ <answer number>

Also u can get answer list from NPC with .lansw or .lsa

You can read more about in-game usage here