After Sauron's defeat in The Battle of the Last Alliance his most powerful servant called the Witch-king, Lord of the Nazgûl fled to the Lands north of Misty Mountains. Over a thousand years have now past and the return of Sauron is near but before he can return once again to the world, the Witch-king needs to dominate the northern reaches of Middle-earth and defend his mighty stronghold against the forces of the Good.
The Rise of the Witch-king is the official expansion pack for The Lord of the Rings: The Battle for Middle-earth II. It introduces Angmar as the seventh playable faction, and a new singleplayer campaign which focuses on it, and which precedes the events of the Lord of the Rings trilogy. All six previously available factions now have access to new units and heroes.
The Create-A-Hero feature is expanded with the new Olog-hai class which consists of three troll subtypes, as well as new customization options for existing classes. There's also a new feature called "Variable Hero Cost" which allows players to gauge the recruitment price of their heroes.
The War of the Ring mode now has two new historical scenarios and the world map got an overall update to fit the new Angmar faction and the unplayable Arnor army that is present only in select scenarios.