Aura Barrier is a Cabal Online skill learned by Warrior, Blader from class rank 6. Description as it appears in the game:
Increase Defense using your aura
Classes that learn it
Other Warrior skills at rank 6
These unlock at the same class rank, so the same quest gives you all of them: Sword Cannon.
FAQ
What does Aura Barrier do in Cabal Online?
Increase Defense using your aura
Which class learns Aura Barrier?
Aura Barrier is learned by Warrior, Blader. It unlocks at class rank 6.
How do I raise my class rank?
Through the class rank quests the game offers every few levels. Each rank opens new skills and, later on, the Battle Modes.