Having been trained in the best spots to strike and how to reach them, you learn how to deal additional damage when the time is right. Similar to the Rogues "Sneak Attack" class feature Once per turn, you can deal an extra 1d6 damage to one creature you hit with an Attack f you have advantage on the Attack roll. The Attack must use a Finesse or a ranged weapon.

You don't need advantage on the Attack roll if another enemy of the target is within 5 feet of it, that enemy isn't incapacitated and you don't have disadvantage on the Attack roll.

This extra damage is 1d6 at level one and increases to 2d6 at level 6, then again to 3d6 at level 13.