Your focus is on the mastery of weapons and their craft. Some arms masters see themselves as collectors, adventuring in search of rare and exotic weaponry which they can use to flaunt their status, as well as to better arm themselves for combat. Others have already found their perfect weapon, whether it be an ancestral blade passed down through generations or a great club made from scrap held together with nails, to these people their weapon is as much a part of their personality as it is a tool for violence.

As an arms master, you might have been a gladiator, seeing your weapons as a means to create even greater spectacles for your audience. Maybe you're a weapon snob, seeing those who wield weapons that you deem lesser as simpletons and fools. Or perhaps you fit none of the preconceptions that others might have about arms masters, instead opting to forge your own path with your weapons close at hand.

Mastered Weapons

When you choose this archetype at 3rd level, your focused training grants you mastery over a select few weapons.

Choose three weapons to be your Mastered Weapons. Each of these weapons can be any simple or martial weapon that lacks the special property. The lance is also a valid choice. If your Dungeon Master uses the rules on firearms in the Dungeon Master’s Guide, they are also a valid choice. You gain proficiency with these weapons if you don’t already have it. When you reach 9th, 13th, and 17th level in this class, you can choose an additional weapon to be a Mastered Weapon for you, following the criteria above.

Master Combatant

Also at 3rd level, you learn how to better attack your enemies and protect yourself in combat. You gain the following benefits.

Deft blows. When you make an attack with one of your Mastered Weapons, you can use your Sneak Attack even if the weapon lacks the finesse property and is not a ranged weapon. You must still meet all other criteria to be eligible to use Sneak Attack. In addition, you can draw one of your Mastered Weapons as part of an attack you make with the weapon.

Armored Fighter. You gain proficiency with medium armor and shields.

Weapon Knowledge

Starting at 3rd level, you gain a deeper understanding of weapons and the process of crafting and maintaining them. 

You gain proficiency with smith’s tools. Your proficiency bonus is doubled for any ability check you make that uses this proficiency.

In addition, when you make an ability check to determine a weapon’s origin, you have advantage on that ability check.

Masterwork Weapons

Starting at 9th level, you gain the ability to improve the craftsmanship of any weapon you have mastered. 

As part of a long rest, provided you have smith’s tools in hand, you can choose up to 3 individual weapons that are your Mastered Weapons, spending 10 minutes per weapon to improve them. These weapons become your Masterwork Weapons until you use this feature again to choose different weapons. 

While you are wielding one of your Masterwork Weapons, it has the following additional properties:

• When you use your Sneak Attack as part of an attack you make using this weapon, you deal an additional 1d6 Sneak Attack damage. This bonus increases to 2d6 when you reach 13th level, and 3d6 when you reach 17th level in this class. 
• This weapon gains a +1 bonus to its attack and damage rolls, unless it is a magic weapon that already has a bonus to those rolls. This bonus increases to +2 when you reach 13th level, and +3 when you reach 17th level in this class.
• This weapon counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.

Mastered Weapon

When you reach 9th level in this class, you can choose another type of weapon to be a Mastered Weapon for you, following the criteria above.

Weapon Tactics

At 13th level, you learn how to utilize different fighting styles to complement your weaponry of choice. 

When you finish a long rest, you can learn one Fighting Style option of your choice from the fighter class. If you already have a style, the one you choose must be different. You lose the Fighting Style granted by this feature when you use this feature to choose a different Fighting Style that you lack.

Archery

You gain a +2 bonus to attack rolls you make with ranged weapons.

Defense

While you are wearing armor, you gain a +1 bonus to AC.

Dueling

When you are wielding a melee weapon in one hand and no other weapons, you gain a +2 bonus to damage rolls with that weapon.

Great Weapon Fighting

When you roll a 1 or 2 on a damage die for an attack you make with a melee weapon that you are wielding with two hands, you can reroll the die and must use the new roll, even if the new roll is a 1 or a 2. The weapon must have the two-handed or versatile property for you to gain this benefit.

Protection

When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.

Two-Weapon Fighting

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack.

Masterful Strikes

Starting at 13th level, you gain a greater understanding of how to best make attacks with your Mastered Weapons.

You gain access to the following Masterful Strike options. You can only use one Masterful Strike option per turn.

Lacerating Strike. Once on each of your turns, when you deal slashing damage to a creature with a Mastered Weapon, you can choose to make a Lacerating Strike.

When you make a Lacerating Strike, the damaged creature’s speed is reduced by 10 feet, and it cannot take reactions. These effects last until the start of your next turn.

Staggering Blow. Once on each of your turns, when you deal bludgeoning damage to a creature with a Mastered Weapon, you can choose to make a Staggering Blow.

When you make a Staggering Blow, you can move the damaged creature 5 feet to an unoccupied space, provided the creature is no more than one size larger than you. In addition, the next attack roll against the creature has advantage if the attack is made before the start of your next turn.

Precision Shot. Once on each of your turns, before you make an attack roll with a Mastered Weapon that deals piercing damage, you can choose to make a Precision Shot.

When you make a Precision Shot, your attack scores a critical hit on a roll of 19 or 20. In addition, you ignore half cover and three-quarters cover for this attack.

Mastered Weapon

When you reach 13th level in this class, you can choose another type of weapon to be a Mastered Weapon for you, following the criteria above.

Flawless Technique

At 17th level, you have perfected your technique with your Mastered Weapons.

When you use your Sneak Attack as part of an attack you make using one of your Mastered Weapons, you can treat any rolls of a 1 or 2 on your Sneak Attack dice as a 3.

Mastered Weapon

When you reach 17th level in this class, you can choose another type of weapon to be a Mastered Weapon for you, following the criteria above.