FISSION Critter Modding Mini-Guide

Add a Custom Critter (NPC, Creature, or Enemy)

This guide assumes you have a working mod folder (e.g., mods/mod_mytown.dat/ from the Quick Start Guide). You’ll add a new NPC that can be placed on maps, fight, talk, or follow the player.

1. What You Need

Your existing mod folder: mods/mod_mytown.dat/ (a folder for development, compress into actual .dat for release)

You will create two new files for your critter:

• proto/critters/critters_mytown.lst – lists your custom critter file(s)
• text/english/game/pro_crit_mytown.msg – provides name and description

Plus the actual .pro file – you can export it from the Mapper or copy and modify an existing one.

2. Create the Proto Definition File

File: mods/mod_mytown/proto/critters/critters_mytown.lst

myguard.pro

Each line is the name of a .pro file (without path). You can add multiple lines for several critters.

Optional Overrides

After the filename, you can add key=value pairs to override certain fields:

myguard.pro fid=450 ai=3 script=12

Why overrides? They let you reuse a base .pro file (e.g., a “human guard” template) but give it a unique look, AI, or behavior using mod assets. Currently the mapper.exe will not support assets in beyond the vanilla games base.

3. Create the Message File

File: mods/mod_mytown/text/english/game/pro_crit_mytown.msg

Each critter gets two consecutive entries: name then description.

{0}{}{Town Guard}
{1}{}{A well-armed protector of the settlement.}
{2}{}{Bandit Leader}
{3}{}{The ruthless boss of a raider gang.}

• The first critter (myguard.pro) will use offsets 0 (name) and 1 (description).
• The second critter (second line in .lst) would use offsets 2 and 3, etc.

Note: The base ID for these messages is generated automatically from your mod name (mytown) and the type (crit). You don’t need to calculate anything.

4. Where to Put the .pro File

The .pro file must be placed in the same folder as the .lst file:

mods/mod_mytown/
        └─  proto/
            └─  critters/
                    ├─ critters_mytown.lst
                    └─  myguard.pro

How to get a .pro file:

• Option A: Use the Mapper - open the Proto Editor, create a new critter, save it as myguard.pro in the mod’s proto/critters/ folder.
• Option B: Copy an existing vanilla .pro (e.g., from proto/critters/) into your mod folder and rename it. The PID inside the .pro file is ignored – FISSION generates its own stable PID from the mod name and filename.

5. Test Your Critter

1. Run the game once (or reload if already running).
2. Check data/lists/proto_list.txt – your critter should appear under “CRITTER MOD PROTOS”.
3. Find the generated PID (e.g., 33686018). You can now use it in scripts:

variable npc_pid;
npc_pid := 33686018;   // use the number from proto_list.txt
create_object(npc_pid, tile, elevation);

6. Important Notes

PID generation is stable – the same mod name + proto name always produce the same PID. You can safely hardcode the PID from proto_list.txt in your scripts.

The PID inside the .pro file is ignored – do not worry about what number it shows.

Hash collisions – if two different mods accidentally generate the same PID, a warning message box appears and the second critter is skipped. Rename your mod or proto to resolve.

Message IDs – each critter uses two consecutive IDs (name, description). The base ID is allocated per mod, so you never need to assign numbers manually.

AI packets – Standard AI packets are defined in ai.txt (vanilla: 0 = none, 1 = coward, 2 = aggressive, etc.). You can also add custom AI packets via ai_mytown.txt.

7. Quick Troubleshooting

8. What’s Next?

Once your custom NPC is working, give it a unique combat personality with the AI Mini‑Guide. You can define aggression, weapon preferences, taunts, and even disposition variants (coward, defensive, aggressive, berserk) that respond to the ai_set_disposition script command.