Regain hit points equal to 1d10 + 20 as a bonus action, once per short or long rest.

Spend one superiority die and use a bonus action to direct an ally to strike, letting that ally use its reaction to make one weapon attack.

Make one weapon attack as part of the Attack action, benefiting from any Battle Master maneuver she chooses to apply.

Take one additional action on her turn, usable twice before a short or long rest at high level.

Spend one superiority die to add it to an attack roll before or after rolling, but before the DM says whether the attack hits.

Spend one superiority die to make a melee weapon attack after a creature misses her with a melee attack.

Spend one superiority die to add it to damage and force the target to make a Strength save or fall prone.

Spend one superiority die to add it to damage and force the target to drop one held object.

Spend one superiority die to add it to damage and push the target away from her.

Spend one superiority die to add it to damage and frighten the target if it fails a Wisdom save.

Spend one superiority die to reduce the damage of a melee attack that hits her by the die plus her Dexterity modifier.

Spend one superiority die to add it to damage and force the target to make a Wisdom save or attack her on its next turn.

Brenna has proficiency with all armor, shields, and martial weapons.

At 3rd level, Brenna chooses the Battle Master martial archetype, gaining Combat Superiority, superiority dice, and maneuvers that let her control the battlefield with precision, teaching force, and tactical flexibility.

She learns three maneuvers at 3rd level, plus additional maneuvers at 7th, 10th, and 15th level, for a total of nine. Her maneuvers are: Precision Attack, Riposte, Trip Attack, Disarming Attack, Pushing Attack, Menacing Attack, Parry, Goading Attack, and Commander's Strike.

She has four superiority dice, which are d12s at 18th level. She regains all expended superiority dice when she finishes a short or long rest.

She can spend a short rest training or studying another creature to learn approximate combat capabilities, making her unusually effective at judging strength, armor class, hit points, class levels, and fighter levels.

Years of disciplined discipline and battlefield study grant her proficiency with one type of artisan's tools, in this case calligrapher's supplies used for lesson plans, notes, tactical diagrams, and formal instruction.

She has the Extra Attack feature, allowing her to attack twice whenever she takes the Attack action. At 11th level this increases to three attacks, and at 20th level she makes four attacks whenever she takes the Attack action.

Beginning at 9th level, she can reroll a failed saving throw. She can do this once per long rest at 9th level, twice per long rest at 13th level, and three times per long rest at 17th level.

At 10th level, if she has no superiority dice remaining when she rolls initiative, she regains one superiority die.

She gains the Ability Score Improvement feature at 4th, 6th, 8th, 12th, 14th, 16th, and 19th level, for a total of seven improvements. Brenna used them to perfect her physical conditioning, tactical intellect, and battlefield awareness.

At 20th level, she can make four attacks whenever she takes the Attack action.

Thanks to her rank and cultivated reputation, Brenna can secure access to people of influence, social gatherings, and the practical privileges that come with recognized station. She is treated as a person of importance rather than a common laborer, and can usually obtain audiences or modest shelter from those who respect titles and pedigree.