The first step in making a custom NPC is to add an additional NPC to the data\npcs.txt file found in the unpacked game data. First, the NPC must be named; NPCs in game are named based on order of appearance, and race. Skeleton NPCs are named NPCx (where x is a unique number to differentiate them), Light Blob NPCs are named NPCBx, Ghosts are named NPCGx, Dark Blobs are named NPCDx, cameos such as Steven and Isaac, from Edmund’s other games are named NPCXx, and finally the large Stevens that transport Ash to the future are named NPCHx. Therefore custom NPCs should use a unique naming scheme, such as NPCAx, to prevent your mod from editing and conflicting with in-game NPCs.
The basic description, such as #basic sideways that appears below the name has no effect and is used to identify NPCs.
The movieclip decides what form your custom NPC takes.
sound_id is similar, and decides the noises your NPC makes when it’s dialogue activates. These are fairly descriptive, such as NPCSkull making a bone-rattling noise when spoken to. Generally, the sound_id should match the movieclip.
The text decides what your custom NPC says when spoken to. Each set of double-quotes "" is a separate box of text that appears in sequence. The new-line character \n makes the text after it start on a new line. Text should be surrounded by square brackets [], and dont forget to add curly brackets {} brackets around your NPC’s code, or else an error will occur when you enter the level.
Here is an example of what an NPC entry could look like when complete:
01 NPC0 {
02 #basic sideways
03 movieclip NPC0
04 sound_id NPCSkull
05 text [
06 "oh \n . . . \n its you. . ."
07 "must be nice \n being alive \nn' all that"
08 "when i died \n that tumor wiggled out"
09 "it's been floating \n up there for years \n watching me"
10 "please\n dont take it. . . \n its all i have left"
11 ]
12 }
To add your NPC to a level, you must add your NPC to the level’s data\tilesets.txt code. The NPC’s name should be written after npc_1, npc_2 or npc_3. Then, add your npc to the level using the level editor; NPCs are found in tiles Z1 - 3 in the editor, in order of number. See the Tile Reference for more information on these particular tiles.
After finishing the Getting Started / Tutorials section, please see the Modding Reference and particularly the NPCs section for more information on the possible values and details regarding custom NPCs.