I've been really excited for the long-awaited Early Access release of Mount & Blade II: Bannerlord. While the official modding tools and documentation aren't available yet, some of us are digging around in the DLL with tools like DotPeek (JetBrains), and figuring out how to make alterations to the game with community documentation.
It's been a lot of funning learning how to use Harmony too, which is a DLL for run-time method patching in C#. I used it in my own project to add commands to the OnMissionTick method of the MissionBehavior class, using Harmony's Postfix() patch option. This way of adding funtionality will continue to be compatible with other mods as they're released, because I didn't alter the core functionality of the built-in method, but merely hooked something to run after it executes.
The mod can be found here:
https://www.nexusmods.com/mountandblade2bannerlord/mods/146
More information about Harmony 2.0 can be found here:
https://harmony.pardeike.net/
DotPeek from JetBrains can be found here:
https://www.jetbrains.com/decompiler/