Configuring Visual Studio
Introduction
Plugins are DLL files containing custom C# code for the game. It allows modders to do custom logic and advanced stuff.
To create a plugin, you need to download and use Visual Studio and have some notions of C# programming and Unity.
Configuring Visual Studio
First create a new class library (.net framework) project in Visual studio.

Once done, you need to reference the Unity and game dll.

What you need here is relative to the thing you want to do, but a good start will be adding these references:
- UnityEngine.dll - Unity engine
- UnityEngine.CoreModule.dll - Unity core module
- UnityEngine.PhysicsModule.dll - Unity physic module
- Assembly-CSharp.dll - Game code

After that, you should be ready to code. To get started, please read the documentation about Item/Level modules and take a look at some examples like the Witch Broom or Shock blade