Ulkair
Ulkair is an incredibly powerful Great Unclean One and one of the main antagonists of Dawn of War II: Chaos Rising.
Backstory
A thousand years before the setting of Chaos Rising, Ulkair engulfed Planet Aurelia into a warp storm, pushing the planet away from its orbit and causing it to become a frozen wasteland. Ulkair was then confronted by Moriah of the Blood Ravens, who managed to wound the Great Unclean One before dying by stabbing through his heart. Moriah's student, Azariah Kyras, finished Ulkair off and imprisoned the mighty daemon into Aurelia, where it remained trapped until the invasion of the Black Legion.
Despite being trapped, Ulkair's influence was still felt by Kyras during his time in the Judgment of Carrion, which would eventually lead him into becoming a corrupted member of Chaos.
Involvement
Dawn of War II: Chaos Rising
As the Black Legion invaded Subsector Aurelia, Eliphas the Inheritor and his minions went on a quest to capture several Space Marines which would serve as a sacrifice to break Ulkair's prison. Manifesting into the body of a Plague Marine, Ulkair start to break his prison, which caused Planet Aurelia to be torn apart.
The Force Commander and his squads would be then tasked to defeat the Daemon before it freed himself with the aid of Gabriel Angelos and his own forces. As the Force Commander passed through the forces of Chaos and defeated Eliphas in battle, they eventually became face-to-face with the Daemon itself. After a long and hard battle, Ulkair was once again defeated and imprisoned, but remarked that his prison was cracked and weakened, and he would soon rise again to destroy the Blood Ravens.
Dawn of War II: Retribution
Despite his defeat by the hands of the Force Commander, Ulkair's presence was still active in Aurelia, where it corrupted the minds of several Imperial Guardsmen on the planet.
On all campaigns, an optional mission is available which takes place at Ulkair's prison. His whispers can be heard in certain parts of the map, and hundreds of traitor Guardsmen defended his prison with great zeal.
If this mission is played in the Chaos Campaign, Eliphas will once again free Ulkair from his prison. Ulkair then joins Eliphas's forces against Kyras, unlocking the Great Unclean One for the player to summon on the field.