Combat ability doubles the critical threat range with a given weapon. A longsword that normally threatens a critical on a roll of 19-20 would now threaten a critical on a roll of 17-20. The threat range of a Keen weapon is already doubled, and is not further improved with this feat. This feat can be selected multiple times, applying to a new weapon category each time. Special: Halflings and Gnomes are small creatures and as such they can never use the following large weapons: greataxes, greatswords, halberds, scythes, spears, and warmaces.