I wanted to use the leap motion device to control my own rigged hand in Unity. I saw online that I maybe need to use the HandController prefab in the Core assets but there was no such prefab.
Can you point to the documentation you're referencing?
It mentions using HandController. I think I am supposed to use it to control my rigged hand in unity below:
This is the documentation for our older V2 software; assuming that you're using our most recent Unity assets, you want the latest and greatest: https://leapmotion.github.io/UnityModules/hands-module.html