Battle Aura (闘気 Tōki, lit. "Fighting Spirit") is a technique used to amplify physical capabilities of the individual to the extreme
Battle Aura, in essence, is a form of Mana manipulation, but different from the flashy effects of Magic invocation as it is invisible to the naked eye. It is specifically used as a technique to explosively boost physical power and physical defense. It involves coating the whole body or a specific body part in Mana and forming a mantle of dense energy.
It does not have a specific training regime, an individual will naturally come to understand how to wear Touki the more they train their body. In the case with Rudeus, he is unable to understand how Touki functions, similar to how he doesn't understand healing magic; as a result, he is unable to use it. This is attributed to the Laplace factor as Laplace was also unable to use Touki, but some, such as Sylphy, are able to.
All swordsmen and fighters at or above Saint-class are able to wear Battle Aura. Some use it unconsciously as to why they cannot explain their impermanent outbursts of strength during battle.
Battle Aura is typically used by all swordsmen. Wearing Battle Aura is woven into the art of swordsmanship, it worked to improve one's physical prowess and strengthening the metal of the sword itself. Swordsmen whose Battle Aura has been fully developed are able to cleave boulders in a single stroke, or unleash a flash of the blade to strike a distant foe.
Other than swordsmen, Warriors, Knights, and martial arts practitioners also wear Battle Aura to enhance their weapons' durability and physical attack.
Instinctively, swordsmen and fighters sheathe themselves in a protective veil of Battle Aura around the user's body or a specific body part. When mastered, the veil of Battle Aura can become impenetrable to most physical attacks.
It also greatly elevates one's sense of the battlefield.
- Saint Dragon Battle Aura (龍聖闘気 Ryūshō Tōki): The greatest combat technique of the Dragon Tribe created by the Dragon God Urupen.
It is a style that uses relatively less Mana, and boasts an overwhelming defensive power that only attacks of very high caliber are able to leave an effect on the user.
- Demon God Laplace was one who was unable to wear Battle Aura.
- Those born in the future with the Laplace Factor after Laplace's sealing are all inherently unable to wear Battle Aura.