The deities of the core D&D pantheon span the spectrum of both alignment and temperament. Their clerics display equal variety when it comes to domain spells, customs and codes of conduct.
Why should a cleric of a wild warrior deity like Gruumsh or Kord equip himself in heavy armour, or even learn its use, when his barbaric flock enters battle with only fury and courage for protection?
The archetypical D&D cleric, with his mace and full plate displayed as prominently as his holy symbol, is as much a warrior as a spellcaster. In a similar vein, the rage cleric presents his divinely-inspired fighting arts just as proudly, although they take a very different form.
A rage cleric has the barbarian’s rage ability. Although this greatly increases his melee prowess, it also limits his spellcasting ability in the heat of combat. The rage cleric’s lower base attack bonus and d8 Hit Dice make him a far less effective frontline fighter than a barbarian, but if he prepares himself with spells beforehand he becomes a formidable berserker.
Most rage clerics follow deities who grant access to the Chaos, Strength and War domains. On rare occasions, neutral clerics of lawful war deities adopt this class, but such wild warrior-priests walk a fine line between losing their deities’ favour and capitalizing on their signature ability.
Rage clerics often begin their careers as barbarians, but at some point they experience a spiritual awakening that leads them down the path of the faithful.
Humans, dwarves and half-orcs make up the majority of rage clerics. Elves, although chaotically inclined, usually lack the inner ferocity necessary to turn that chaos into a barbaric rage. Orc clerics, on the other hand, almost always adopt this variant class, which personifies the will of their barbaric deities. Many savage humanoids and lesser giants also favour it.
The rage cleric is a variant cleric. Unless otherwise noted, a rage cleric advances in the same manner as a cleric (same Hit Die, base attack bonus, saving throw bonuses, skill points and so on). When a character elects to take a level of cleric or rage cleric, he may not later take levels in the other class. This prevents the character from gaining the benefits of a 1st-level cleric twice.
Alignment: A rage cleric cannot be lawful but must still be within one step of his deity’s alignment.
All of the following are features of the rage cleric class.
Weapon and Armour Proficiency: A rage cleric is proficient with all simple weapons, light armour and shields (except tower shields).
Rage: A rage cleric rages as a barbarian of equal level and gains the greater rage, indomitable will, tireless rage and mighty rage class features as he progresses. Rage cleric and barbarian levels stack for the purposes of determining the number of times per day a character can enter a rage and the type of rage variant available.
In exchange, a rage cleric loses his ability to turn or rebuke undead as well as his ability to gain domains (which includes domain granted powers and domain spells).
A rage cleric who becomes lawful loses his rage abilities. However, provided that his deity accepts lawful-aligned clerics, he can continue to advance in this class and gain spells.
A rage cleric who grossly violates the code of conduct required by his deity (generally by acting in a manner contrary to the deity’s alignment or purposes) loses all spells and class features, except for rage and proficiency with light armour and simple weapons. He cannot continue to advance in this class until he atones (see the atonement spell).
Source: Dragon Magazine #333 (Page 86)