Enhanced Physical Prowess
To many, there is hardly any difference between the standard Soldier and a Fighter save for skill, this of course is absolutely not the case. But the Fighter rarely bothers to correct this mistake, there is exists no greater freedom than to be constantly understimated. Then again, if they bothered to tell them the difference would they at all believe what they heard? Doubtful, for few can fathom that these combatants possess such raw physical capabilities as to fight toe to toe with some of the most fearsome beasts in the world, with nothing but their raw physical capabilities and strength of character.
The difference between a Fighter and the regular Soldier is that unlike the latter, Fighters don't wield weapons in combat but their own spirit, the weapons they wield merely serve as a focus for this inner energy; and in truth Fighters are capable of incredible feats even if they are somehow disarmed. When properly channeled, this energy - labelled as their aura by Scholars. Allow them to ignore the physical boundaries of the human body, eventually becoming capable of easily performing superhuman feats of endurance, durability and strength.
Fighters develop their aura by first training their mind, only begining to train the body after they've mastered the spiritual aspects of their martial prowess, this way their aura is awakened and they can reach for it in order to perform fantastical feats. Since Fighters use their spiritual self to do battle, rather than their physical body - they're capable of trancending the restrictions of the human body entirely and the strain they leave on their bodies is therefore lessened significantly. With time and experience, a Fighter can discover the means to reduce the strain on their body so much, that it becomes almost non-existant, allowing them to fight as easily in their empowered state as if it was the natural state of their bodies.
When their Aura is exerted in battle, it gives the Fighter access to a select few abilities, whom, while few in number can be modified and improved at the leisure of an individual Fighter. The most famous of these; and one which commonly makes ignorant people confuse them for spellcasters of a sort. Is the so-called 'Vacuum Blade', a technique which relies on incredible strength and alacrity; allowing the Fighter to turn the very air itself into a weapon, a vorpal blade of pure wind pressure designed to strike down an enemy from afar.