"I have had a hard life and a long; and the leagues that lie between here and Gondor are a small part in the count of my journeys. I have crossed many mountains and many rivers, and trodden many plains, even into the far countries of Rhun and Harad where the stars are strange."
Rhun is a large region in the East of Middle-earth occupied by the Easterlings. These people were allied with Sauron and sent many fierce warriors to fight for him during the War of the Ring.
In the Edain Mod, the soldiers of Rhun can be used when the 'Reinforcements from Rhun' spell has been bought with Mordor. This allows the player to summon the elite Rhunic soldiers (command points are needed) who march in from outside the battlefield. The Black Easterlings can be summoned using Khamul's level 10 ability, Vassals of the Ringwraith.