Needs review
Source: Player's Handbook

Description: You are proficient with certain martial weapons in combat. Prerequisites=

Prerequisites: ,\sNone

Required for: Shards of Earth (Tetsubo)

Choose a type of martial weapon, such as longbow. You understand how to use that type of martial weapon in combat. Use this feat to expand the list of weapons you are proficient with beyond the basic list in the class description. You make attack rolls with the weapon normally.