True power is based on one's ability to control mana, and such control is typically divided into two camps: External and Internal. The external control of mana is magic, and its practitioners are often physically weaker, but have access to powerful external effects. The internal control of mana, however, is less well explored. As a practitioner of internal mana you gain the following abilities:

Martial Essence. For every 2 levels of you have in a Martial class, and every 4 levels you have in a half caster class, you gain 1 point of Martial Essence. You can spend these points to enact different effects, some of which require your character be of a certain level.

• Empowered Movement. You can spend 1 Martial Essence as a bonus action. You gain the benefit of the Dash and Disengage actions and immediately end the Grappled and Restrained conditions on yourself. Until the end of your turn, your jump distance is doubled, fall damage you take is halved, and you are allowed to enact feats of movement prowess otherwise unrealistic. 
• Empowered Attack. When you make a weapon attack, you can spend 1 Martial Essence, which is refunded if you miss. You empower your weapon attack, imbuing it with one of the following effects:
  • Spectral Strike. You add force damage equal to your Proficiency Bonus to the damage roll, and the reach/range of the attack doubles.
  • Forceful Strike. You add thunder damage equal to your Proficiency Bonus to the damage roll, and if the target is 1 size larger than you or smaller, it is pushed up to 15 feet away from you and must make a Strength saving throw. On a failed save, it is knocked Prone.
  • Finishing Strike. You add weapon damage equal to your Proficiency Bonus to the damage roll, and roll a d6. On a 6 the attack becomes a critical hit.
• Renewal (LVL 6). Once per long rest you can spend 3 Martial Essence, focusing for one minute and gaining the benefit of a short rest. You can roll a maximum number of hit dice through this feature equal to your proficiency bonus, and hit dice used in this way are not expended.
• Supernatural Feat (LVL 8). As a part of activating a feature from your Race, Feat, or Non-Full Caster Class you can spend 2 Martial Essence, empowering it. The feature cannot be a spell, you cannot have more than one feature empowered at a time, and you cannot empower the same feature more than once in a single combat. The DM determines the empowered effect of the feature, but must tell you the effect before you commit to using it.
• Exalted Attack (LVL 10). You can expend extra essence when activating Empowered Attack. For each extra point of Martial Essence spent, the empowered effects of the attack double. I.E. Flat damage bonus doubles as does: reach/range for Spectral, push distance for Forceful for which the size limit also increase by 1 per extra point, and the d6 from Finishing becomes a d4 then a d2 then a guarantee. 
• Empowered Ability (LVL 12). You spend 2 Martial Essence as a bonus action. For the next minute you are able to push past the normal limits of your body. You can add +10 to Strength, Dexterity, or Constitution based checks and saves (choose 1 for which your ability score is at least 15) and can accomplish physical feats beyond mortal ability.

When you spend more than 2 Martial Essence in a single turn, you gain a level of exhaustion for each point you spent beyond 2 at the end of your turn. The uses of mana, both internal and external, are legion, and many warriors have built their name though the creative and limit-breaking uses of their essence (feel free to ask your DM about unique uses and effects). Push boundaries and carve your name just as deeply into the world as those who came before you.

Due to the complicated nature of obtaining Martial Essence points, you will have to track them yourself. Their application is beyond DnDBeyond's ability.