Thundering Rage

From NWN2Wiki

Type of feat: General, Epic

Prerequisite: Character level 21, Rage 5/day, Strength 25

Required for: None

Specifics: Any weapon the barbarian wields while in a rage does an additional 1d8 (2d8 if multipier is X3, 3d8 if multiplier is X4) points of sonic damage on a critical hit. There is a 50% chance for a creature hit by one of the barbarian's weapons to be deafened for 3 rounds.

This feat seems to be treated as a Barbarian only class feat, preventing you from selecting it except on a Barbarian Class level.

Gameplay note: Rage 5/day class feat is gained at a Barbarian's 16 class level. Extra Rage feat does not count towards the requirement.

Use: Automatic