If you are downloading v1.0.0.3 for a mod, download the files from a repository like Nexus Mods or the Steam Workshop.
Extract mod files into the Modules folder within your main game directory (e.g., SteamApps/common/Mount & Blade II Bannerlord/Modules ). Download Mount and Blade II Bannerlord v1.0.0.3...
Depending on which version you are targeting, here are the highlights: If you are downloading v1
Early versions of the v1.0.3 "Conqueror" update introduced new cultures for players, allowed recruitment of Clan troops, and moved bandits into their own faction to better control their spawns. allowed recruitment of Clan troops