The Arcane Marksman came about when warfare changed from sword and shield to rifle and trench. Each Marksman is equipped with special weapons known as Mana Rifle and Pistol they use mana to power their projectiles rather than using gunpowder allowing for greater flexibility in firearm warfare. 

Marksman's Arcane Ward

At 2nd level, you have learned to weave your magic to fortify yourself against harm. When you are hit by a spell attack or you fail a saving throw from a spell, you can use your reaction to gain a +2 bonus to your AC against that spell attack or a +4 bonus to that saving throw.

When you use this feature, you can’t cast spells or use your Mana Arm until the end of your next turn, you may use cantrips however.

Mana Arms

At 3rd level, you gain proficiency with Mana Arms and Tinker's Tools. 
Mana Arms use your Intelligence modifier instead of Dexterity to add damage and accuracy.

Overcharge

Starting at 2nd level, you can overcharge your Mana Rifle dealing extra damage in exchange for a chance to have mana feedback. When Overcharging a Mana Arm you can use one additional charge to change the damage type (Fire, Cold, Thunder, or Lighting) or add an additional die of the base damage, you can increase the amount of Charges used up to four charges, however for each additional charge used in Overcharge you chances for Overload increase. 

Overload. Roll a d20 to determine the outcome the DC is 10+ Charges Used+ Overcharged uses, Overcharge uses reset after a short rest.

• Success. The weapon can be fired normally.
• Failure. For each additional charge used in Overcharge, a round must pass for the weapon to cool down.
• Critical Failure. On a Natural 1 the weapon explodes dealing 8d6 force damage in a 20 foot radius, the damage is increase by 1d8 for each additional charge over 2 added to the Mana Arm. Each creature must make a dexterity saving throw DC 10+amount of charges on a success takes have damage. Each creature Large and smaller is pushed 5 feet away from the center.

Double Tap

Starting at 6th level, when you use your action to fire your Mana Rifle, you can fire again as a bonus action.

Weak Point

At 10th level, you learn how to pick out weak spots on your targets. When you attack a creature with a shot from your Mana Rifle, that creature has disadvantage on the next saving throw it makes against a spell is cast on it before the end of your next turn.

Mana Stability

At 14th level, when rolling for the overcharge outcome of your Mana Rifle you have advantage.