Upon plundering a settlement:
- Prosperity is reduced by 25%
- Loyalty is reduced by 75%
- Security is reduced by 75%
- City's traders will lose 80% of their denars
- Relations with a settlement's notables will be lowered.
- Relations will be lowered with all clans of the same culture as the settlement.
- Your plundered wealth: The total plunder will be worth 1000 gold per prosperity point plus 80% of a city's trader's denars. Your personal share is 50% of the total, as your warband gets the other 50%.
- Party morale is increased as "recent events" by 1 per 4000 gold of plunder. Note that "recent events" in vanilla is capped at +50.

Notices:
- Plunder report messages will be shown at the bottom left.
- You can only plunder a settlement if you are the leader of the army that takes it.
- As a side effect of a workaround I had to use, you'll be teleported into a settlement after conquering it. When leaving, you are teleported back.
- The AI does not make use of this mod.

Todo:
- Colour the reports at the bottom left.
- Cause collateral damage, lowering the level of random buildings.
- Enable the AI to also be able of committing this war crime.

Compatibility:

Safe to add and remove mid-game.

Harmony-patches GameMenusCallbacks.menu_settlement_taken_on_init by postfix.

Installation:

Same as for any other module. Unzip it and place it in the game's install folder "...\Mount & Blade II Bannerlord\Modules".
If on Steam, right click the game title -> "manage" -> "browse local files". Both Zip and 7zip downloads available.
If it is installed correctly you'll get a notification text on the bottom left of the screen at the main menu.

Troubleshooting: Troubleshooting Guide

How to report a bug/CTD: Link

Sourcecode: Included in download.

All my mods: Click Here

Credits & Aknowledgements:

- Makes use of Harmony
- Basilisk Guild's sourcecode was an useful example of how to mod menus.
- Cheyron for letting me know how to affect morale.

Disclaimer: War crimes are bad. Do not try this at home.