The Armsmaster specializes in using many different weapons simultaneously. Either through dual wielding or simply attacking many times with a new weapon every time.

Adaptibility

You've learned how to turn your mastery of weapon variety into damage. When you make an attack, if you have attacked the same target with a different weapon this turn, deal additional damage equal to half your proficiency modifier for each other attack made this turn.

Peak Performance

You've managed to make the most out of your state after you are fully rejuvenated. As long as your HP is full, you my reroll any damage rolls you make once.

Master of Offence

You practiced how to transform ever bit of defense you give up into sheer power. As long as your armor class is below 15, you may use change any dice used in a damage roll you make into a d8.

Sixfold Strike

After long and difficult training, you have master the Sixfold Strike, a special move only the greatest Armsmasters can use. As an action during your turn, you can choose an enemy in melee range and make 6 attacks on it in quick succession. Each attack must be made with a different weapon and only one weapon. You don't have disadvantage for using bows or lances on a target within 5ft.

Arms Refinement

You learned how to refine and strengthen your weapons to their maximum potential. The dice that master of offence replaces your attack rolls with is now a d10 instead of a d8.