Rites of War is a game of Warhamer origin, of a defence and conqest by the Eldar race in the 41st Millenium.  The player, in control of the Eldar race, must first defed their lands against the mightly onslaught of the Space Marines (genetically engineered humans) and then, with their aid, cleanse the scourge of the Tyranids, a race of aliens fighting with biological weapons.  As the game progresses, so the game becomes harder.  This is combated by the fact that as one wins scenarios, you earn more glory to purchase more units and more diverse units are unlocked.  These units, as they fight in campaigns and cleanse their enemy's souls, they earn experience and that allows them to become more skillful, attain psychic powers, special abilities and turn into exarchs, more powerful and skillful single entities.