The Elder Scrolls IV: Knights of the Nine

Knights of the Nine centers on a faction of the same name, devoted to locating and preserving a set of "Crusaders' Relics". Once found, these relics must be used to defeat the sorcerer-king Umaril, who seeks revenge on the Nine Divines. Knights of the Nine was generally well received in the gaming press. Although it made little change to the basic mechanics of Oblivion, it was judged by reviewers to be a brief but polished addition to the game's main plot. (Wikipedia.org)