# Modify individual monster spawn rate/cost

**URL:** <https://discourse.cataclysmdda.org/t/modify-individual-monster-spawn-rate-cost/17306>\
**Category:** The Toolbox\
**Created:** [November 2, 2018, 7:18pm UTC](https://discourse.cataclysmdda.org/t/modify-individual-monster-spawn-rate-cost/17306 "2018-11-02T19:18:25Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![TheMurderUnicorn](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/themurderunicorn/32/5706_2.png) [@TheMurderUnicorn](https://discourse.cataclysmdda.org/u/TheMurderUnicorn)\
**Post date:** [November 3, 2018, 10:09am UTC](https://discourse.cataclysmdda.org/t/modify-individual-monster-spawn-rate-cost/17306/7 "2018-11-03T10:09:44Z")

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> [@How to edit monster groups?](https://discourse.cataclysmdda.org/t/how-to-edit-monster-groups/16546):
>
> I’m trying to make a mod that edits the monster groups but I can’t get it working. Lets for example reduce child zombies in schools and add cocroaches instead. So I add a json file in the mod with the following contents (reduced child freq, added cocroach). [ { "type":"monstergroup", "name": "GROUP\_SCHOOL", "default": "mon\_null", "//": "School monster spawns.", "monsters": [ { "monster": "mon\_zombie\_child", "freq": 50, "cost\_multiplier": 1 }, { "monster": "mon\_zombie\_fat", "freq": 50, "co…

That was the thread. It was a brief discussion.

Basically, when you create an entry with the same name, it throws your additions on to the end of that list (as far as I’m aware). I used an example in that thread, but this is what my addition looks like now.

```auto
{
	"type": "monstergroup",
	"name": "GROUP_ZOMBIE",
	"monsters" : [
		{ "monster" : "mon_ravlady", "freq" : 10, "cost_multiplier" : 3 },
		{ "monster" : "mon_zombie_fetus", "freq" : 10, "cost_multiplier" : 2 }
	]
  }
```

This edits the monster group called GROUP\_ZOMBIE and adds those two monsters to that list, as though I had added them directly to the core file. This worked as of about a month ago, though I haven’t fiddled with the mod since then. I don’t see why it wouldn’t still work.

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