Aura is the life energy produced by all living and celestial bodies of the parallel world.

It is the source of 'Card Arts' created by the humans of the parallel world to defend against the racial aura abilities of their otherworld invaders.

There are currently six known ways of using Aura abilities in Card Arts,

1. Innate type card: The inborn aura ability of a Card Master that is unique to them.

2. Enhancement type: Card Masters use aura to strengthen themselves or objects.

3. Morphing type: Card Masters transmute the quality of their aura to match something else.

4. Emission type: Card Masters can detach aura from their body and use it at long range.

5. Control type: Card Masters use aura to manipulate animate and inanimate things.

6. Manifestation type: Card Masters use aura to conjure objects.

Card Master can use aura in the six ways mentioned in the card arts to create cards that grant them different aura abilities.