Per the Core rules: As a champion, you are a warrior in the name of a deity you revere above all others.
In the Viridian region, various orders of Champions exist who are devoted to The Eight as a pantheon of deities, as well as Champions of individual deities. These are small numbers of devotees in most locales, many with an almost cult-like devotion.
In Essodan, one order is well known: The Spellvexxers. These Champions of Harmony hold the Cause of Obedience and work to bring arcane magic users into line. Any other orders are relatively unknown to the average citizen, but they certainly exist.
The Dwarven deity, The Forgemaster, is served by two small orders of Champions who work beyong the Dwarven homelands.
Anathema, Sanctification, Deific Weapon and such can be found under the Cleric entry.
Causes available vary by deity: