Barbarian Rage
Type of Feat: Class
Prerequisite: Barbarian
Required for: Greater Rage
Specifics: The Barbarian may rage, gaining a +4 morale bonus to Strength and Constitution and +2 to all Will saving throws, in exchange for a -2 penalty to AC. The Barbarian may use this ability 1x/day at 1st level, +1/day at 4th level, and every 4 levels thereafter, extending into epic levels
Use: Selected
At 15th level, the rage ability becomes Greater Rage, giving the Barbarian +6 to Strength and Constitution and +3 to Will saves (the -2 penalty to AC still applies).
The duration is the Constitution modifier + 3 rounds. The modifier includes the Rage bonus. For example, a Barbarian with a Con 14 would get +4 to Con 18, which is an ability modifier of 4, so the Rage would last 7 rounds.
Ability bonuses are capped at +12, so if you already gain bonuses from items, spells or potions, you may not gain the full ability bonuses from Rage/Greater Rage.
Barbarian Rage and improved versions of the ability are special versions of free actions that take effect instantaneously, do not require you to momentarily stand still, and do not interrupt other actions that are already in progress, even when used mid-spellcast.