---
title: Customizing Boss Pokémon Spawns in Pixelmon
description: "Learn what every setting in Pixelmon's boss.yml controls. This guide explains how to configure Boss Pokémon spawn rates, rarity, levels, encounter behavior, and other options to customize boss encounters on your Pixelmon server."
source: "https://nodecraft.com/support/games/minecraft/mods/pixelmon/customizing-boss-pokemon-spawns-in-pixelmon"
image: "https://dynamic-assets.nodecraft.com/signedurl/w7vokBAexMnVlnMZ1Q/image.jpg?modifications=W3sibmFtZSI6ImdhbWVfYmciLCJpbWFnZV91cmwiOiJodHRwczovL2Ntcy1hLm5vZGVjcmFmdC5jb20vZi8xMzM5MzIvMjAwMHg1NTAvZGNiMGFkNjkzOC9jYXZlcy1hbmQtY2xpZmZzLXB0LTItMS0yLTAucG5nL20vIn0seyJuYW1lIjoiZ2FtZV9sb2dvIiwiaW1hZ2VfdXJsIjoiaHR0cHM6Ly9jbXMtYS5ub2RlY3JhZnQuY29tL2YvMTMzOTMyLzM3NXgxNTAvM2MxZGIyYmFiNS9taW5lY3JhZnQucG5nL20vIn0seyJuYW1lIjoiY3RhX3RleHQiLCJ0ZXh0IjoiQ3JlYXRlIHlvdXIgb3duIHNlcnZlciEifSx7Im5hbWUiOiJ0ZXh0IiwidGV4dCI6IkN1c3RvbWl6aW5nIEJvc3MgUG9rw6ltb24gU3Bhd25zIGluIFBpeGVsbW9uIn1d&s=b5618c231a7d99c49c817f82dd65faf4859285c2743b61fffc382e370e194a92"
published: "2026-08-12T19:16:43.555Z"
updated: "2026-08-12T19:16:43.555Z"
---

# Customizing Boss Pokémon Spawns in Pixelmon

Learn what every setting in Pixelmon's boss.yml controls. This guide explains how to configure Boss Pokémon spawn rates, rarity, levels, encounter behavior, and other options to customize boss encounters on your Pixelmon server.

The Boss Pokémon Spawn section contains the options Pixelmon uses for this part of the server. Control Boss Pokémon spawn chances, rarity weights, levels, and related encounter behavior.

## Pixelmon Boss Pokémon Spawn Settings

The settings below are listed in the same order as they appear in boss.yml. The table preserves each default and identifies the accepted value type. The Setting column shows a reader-friendly name first, followed by the matching boss.yml key for reference.

| Setting and Config Key | Default and Accepted Values | Description |
| --- | --- | --- |
| Boss Rate boss-rate | Default: 256.0 Values: decimal number | The rate of boss Pokémon in the wild (1/x) not including mega bosses. |
| Ultra Space Boss Modifier ultra-space-boss-modifier | Default: 0.5 Values: decimal number | Modifies the rarity of bosses in the Ultra Space Dimension (bossRate * ultraSpaceBossModifier). |
| Bosses Always Mega If Possible bosses-always-mega-if-possible | Default: true Values: true or false | Whether bosses that spawn must Mega Evolve if they can. |
| Boss Spawn Ticks boss-spawn-ticks | Default: 10000 Values: whole number | How often (on average) a boss Pokémon will attempt to spawn. |
| Boss Spawn Chance boss-spawn-chance | Default: 0.30000001192092896 Values: decimal number | Chance that a Mega Boss spawn attempt will succeed. 1 = 100% |

## Important Boss Pokémon Spawn Setting Notes

### Defaults and Value Types

Boolean toggles, numeric rates, timers, lists, and mappings use different value formats. Preserve the value type shown in the table and keep collection syntax intact when changing boss.yml.

### Settings That Work Together

Several boss pokémon spawn options can affect the same outcome. Review related rates, limits, timers, and lists together before deciding that one value is responsible for a result.

### Testing Changes

- Change one related group of settings at a time so its effect is easy to measure.
- Test the result under the conditions affected by the setting, including relevant dimensions, player states, or encounter types.
- Keep a copy of the previous values so unexpected balance or performance changes can be reversed quickly.

## Final Thoughts

Boss Pokémon Spawn settings are easier to balance when changes are deliberate and documented. Start with the defaults, adjust only what the server needs, and verify the result before moving on to the next group.