Rage

Rage is a class skill in Diablo: Hellfire. It is gained at the start of the game, and cannot be learned from books.

General Information
Rage is a short-term boost to attributes for 12 seconds. After that time, the Barbarian enters a 12 second lethargy phase, when those same attributes are reduced by the same amount. Afterwards a portion of his Life is supposed to be drained, however due to a bug in Hellfire, changing any attribute (such as unequipping an item in inventory) will reset the Life loss.

Duration: 12 seconds of active phase + 12 seconds of lethargy
 * For 12 seconds adds: 2 x Character Level to Strength and Vitality, 1.5 x Character Level to Dexterity, but removes the resistance bonus from levels.
 * For 12 more seconds, during a lethargy phase, decreases Strength, Dexterity and Vitality by the same amount (deducted from normal values).
 * Afterwards the character loses (2 x Vitality) Life, unless any attributes are changed, which restores lost Life (bug).

Even with a bug, Rage is mostly useless spell. While a Barbarian loses nothing permanently from using this, the fact that he suffers penalties during his rest phase is what makes players gauge the skill's usefulness.

Lore
''Training in brute strength and physical force was the norm for Barbarians, with great endurance and vitality being praised. They came to be large people, with flaring tempers which makes the blood of a Barbarian truly boil when he is outraged.''