Barbarian enhancements (history)

Level 1

 * Barbarian's Action Boost I (30s cooldown): Grants 5 times/rest period the ability to receive 20s boosts to weapon damage, damage reduction, or movement speed.
 * Barbarian's Intimidation: Intimidated foes are shaken
 * Barbarian's Power Attack: +1 bonus to damage with Power Attack feat active. (This enhancement will not show up on the list unless you have the Power Attack feat.) Upgrade II should be available at a later, yet unknown, level.
 * Extend Rage I: Rage lasts 25% longer
 * Fast Recovery I: -20% fatigue duration after Rage (There may be a minimum constitution prerequisite for this enhancement.)
 * Skill Athleticism I: +3 on swimming and jumping checks
 * Skill Interaction I: +3 on intimidate and listen checks

Level 2

 * Barbarian Constitution I: +1 Constitution
 * Extra Rage I: Grants an extra Rage during rest periods (upgrades II and III should be available at later, yet unknown, levels)
 * Power Rage I: Additional +2 Strength while in Rage (upgrades II and III should be available at later, yet unknown, levels)
 * Resist Disease I: Grants a +3 bonus to Disease saving throws (upgrade II should be available at a later, yet unknown, level)
 * Resist Poison I: Grants a +3 bonus to Poison saving throws (upgrade II should be available at a later, yet unknown, level)

Level 3

 * Barbarian's Action Boost II (30s cooldown): Grants 5 times/rest period the ability to receive 20s boosts to weapon damage (+4), damage reduction (set to 8, does not stack with the barbarian's permanent DR), and movement speed.
 * Skill Athleticism II: +4 on swimming and jumping checks
 * Skill Interaction II: +4 on intimidate and listen checks
 * Improved Trap Sense I: +2 on all saves vs traps (upgrades II, III and IV should be available at later, yet unknown, levels)

Level 5

 * Barbarian's Action Boost III (30s cooldown): Grants 5 times/rest period the ability to receive 20s boosts to weapon damage, damage reduction, and movement speed.
 * Barbarian Constitution II: +2 Constitution
 * Skill Athleticism III: +5 on swimming and jumping checks
 * Skill Interaction III: +5 on intimidate and listen checks

Level 7

 * Barbarian's Action Boost IV (30s cooldown): Grants 5 times/rest period the ability to receive 20s boosts to weapon damage, damage reduction, and movement speed.
 * Skill Athleticism IV: +6 on swimming and jumping checks
 * Skill Interaction IV: +6 on intimidate and listen checks

Level 8

 * Barbarian Constitution III: +3 Constitution

Level 9

 * Barbarian's Action Boost V (30s cooldown): Grants 5 times/rest period the ability to receive 20s boosts to weapon damage, damage reduction, and movement speed. This enhancement does not appear in the game files and may actually not exist (please confirm).
 * Skill Athleticism V: +7 on swimming and jumping checks
 * Skill Interaction V: +7 on intimidate and listen checks

Unconfirmed

 * Toughness I: this enhancement appears in the game files but has not been confirmed
 * Damage Resistance I and II: these enhancements appears in the game files but have not been confirmed
 * Willpower I and II: these enhancements appear in the game files but have not been confirmed
 * Hardy Rage I, II and III: these enhancements appear in the game files but have not been confirmed
 * Critical Rage I and II: these enhancements appear in the game files but have not been confirmed