Black Flash

Prerequisite: Proficiency with at least one martial weapon

You can enter a heightened state of focus in combat, allowing momentum to carry you toward devastating precision—or catastrophic failure.

• When you score a critical hit, your critical hit range expands by 1 (to a minimum of 18–20), and you gain advantage on attack rolls.
  This benefit lasts until you miss with an attack or score an attack that is not a critical hit.
  These effects stack, expanding your critical hit range and extending advantage each time you score a critical hit while this feat is active.

• When you roll a critical miss (a natural 1), your critical miss range expands by 1, and you have disadvantage on attack rolls.
  This penalty lasts until you successfully hit with an attack.
  These effects stack, expanding your critical miss range and extending disadvantage each time you roll a critical miss while this feat is active.

• If your critical hit range is expanded beyond its normal value, your critical miss range expands by the same amount.

• If your critical hit range would expand beyond your critical miss range, your attacks automatically score critical hits for the remainder of the current combat encounter.

• If your critical miss range would expand beyond your critical hit range, you automatically miss with all attack rolls for the remainder of the current combat encounter.