> For the complete documentation index, see [llms.txt](https://wiki.mypet-plugin.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.mypet-plugin.com/setup-guide/skilltree-creation/what-are-skilltrees.md).

# What are Skilltrees?

Skilltrees are the way to specify when which pet will unlock/upgrade specified abilities.

The Skilltree mechanism is a feature that allows Pets to learn Skills as they level up. You can think of Skilltrees like player classes (Archer, Swordsman, Wizard, etc.) but for Pets.

MyPet 4 ships with [124 default skilltrees](/setup-guide/skilltree-creation/default-skilltrees.md) arranged as a two-tier "Ascension Ladder". They are ordinary skilltrees built with the features described on these pages - fully customizable, and the ascension design itself is optional.

{% content-ref url="/pages/2OSryvXVHkoJgxl8faaI" %}
[Default Skilltrees](/setup-guide/skilltree-creation/default-skilltrees.md)
{% endcontent-ref %}

### Skilltrees (.st.json)

This is a skilltree file. Every skilltree has its own file, which must be in proper json format and placed in the `plugins/MyPet/skilltrees` directory in your Minecraft server.

### Skills

[Skills](/setup-guide/skilltree-creation/creating-custom-skilltrees/skills.md) are the abilities that Pets gain as they level up. Any ability has its own custom option that can be set in the skilltrees.

### Upgrades

An upgrade will change the settings of a skill. It can add a row to the inventory or add more damage.\
Every upgrade is applied on a level rule that determines when it will be applied.\
An upgrade can be applied on fixed levels or on repeating schedules like every 3 levels.

### Inheritance

Skilltrees are capable of inheritance which means if **skilltree** `a` inherits from **skilltree** `b`, **skilltree** `a` will have all the upgrades from **skilltree** `b` in addition its own upgrades.


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