Mercenary

Regardless of your origin, to get where you are, you likely spent the most formative years of your life as an infantry grunt with no rank or privilege to pull you out of the filth. You aren't accustomed to a knight's armor because they gave you a thick, punctured jerkin still drenched with the previous owner's blood. Your daggers and light weapons were of no use in the crush of bodies and armor, and you were too malnourished to wield great weapons or heft a shield. You were pushed onto your first battlefield with only a quarterstaff, as expendable as yourself, but you managed to survive. In fact, you survived again and again, sometimes with a spear, sometimes with a longsword; whatever you could loot or hold onto from each battle. After nearly a dozen battles, you had real skills that most people never live long enough to acquire and which they don't teach to knights with training swords. Still, your abilities went unnoticed as the soldiers around you were constantly slaughtered and replenished in an endless churn, consuming the poor, the convicted, and unfortunate. Your leaders didn't know your name, they didn't know that you had begun felling elite knights, and they offered nothing for your allegiance except for more mud and violence.

That may not be your story, but it should ring familiar to any mercenary of your skill. You are free now and only fight for coin and yourself. You still only wear light armor, preferring the flexibility, and you might carry weapons used by common infantry, but your greatest asset is being underestimated for what you can do with such common contrivances.

Infantry Training

3rd Level Mercenary Feature

As a foot soldier, the weapons did not suit your malnourished frame until you learned to be patient and precise with your attacks rather than attempting to unleash numerous, powerful strikes. You gain proficiency with all versatile weapons. While wielding a versatile weapon with 2 hands, it has the finesse property.

Combat Instincts

3rd Level Mercenary Feature

Your combat instincts occasionally kick in at just the right moment. You can roll a d6 and add it to a failed attack roll, saving throw, or ability check. You may do this a number of times equal to your proficiency bonus, and you regain all expended uses when taking a long rest.

Art of War

9th Level Mercenary Feature

Each battle you survived sharpened your mind and prepared you better for the next. You gain proficiency with the History and Investigation. As a bonus action, you may perform an active Intelligence (Investigation) check to look for weaknesses in a creature within 15 feet of you against a DC of the creature's CR + 10. If you succeed, then you have advantage on attacks against that creature until the end of your next turn. After you attempt to Investigate a creature once, you cannot Investigate the same creature again for 24 hours.

Counter Attack

13th Level Mercenary Feature

When your opponent feels their weapon contact your flesh, and their mind wanders toward victory for just an instant, then you have an opening to strike back. When using your Uncanny Dodge ability against an incoming melee attack, you may make a melee weapon attack in return as part of the same reaction. If you meet the criteria for a sneak attack, you may use half of your sneak attack dice, rounded up, since this is primarily a defensive reaction. However, if you have 50% or fewer hit points remaining, then you may use a full sneak attack if you do not have disadvantage, regardless of other criteria.

Versatile

17th Level Mercenary Feature

Wielding a versatile weapon with 2 hands increases the damage. Everyone knows that, but you've learned to apply it to your sneak attack damage. While wielding a melee weapon with 2 hands, your sneak attack uses d8s instead of d6s.