The material below is Open Game Content from a 3PP Source
Elemental Rage, Greater (Su): While raging, all of the barbarian's critical hits made with melee weapons deal an additional 1d10 points of energy damage (2d10 if the weapon deals ×3 damage on a critical hit, 3d10 if the weapon deals ×4 on a critical hit). The type of this damage is the same as the type chosen for the elemental rage power. A barbarian must have the elemental rage power to select this rage power. A barbarian must be at least 12th level to select this rage power.