UMC add-on SP Campaign for Battle for Wesnoth.
Lich-Lord Jevyan is defeated, and the orcs are left in disarray. With the magical gates from the far East sealed, the warlords resort to their traditional ways—seeking to overcome adversity with blood and razor-sharp steel. Amid this chaos, a cunning assassin named Arshag embarks on a quest to secure a new homeland for his people.
You can get the latest version of the campaign in-game. Click on the Add-ons button in the main menu and connect to the official add-ons.wesnoth.org server. Then search for the name of this campaign and select it for installation.
As of March 2024, the main branch now only supports Wesnoth 1.18. To download the Wesnoth 1.16 version of the game, use the legacy branch.
More info about the campaign on my website. Wesnoth forum post for your feedback. Watch the trailer.