Soul Blade is a Cabal Online skill learned by Warrior, Blader from class rank 3. Description as it appears in the game:
Advanced skill of Blade Aura.
Classes that learn it
Other Warrior skills at rank 3
These unlock at the same class rank, so the same quest gives you all of them: Raging Thrust, Rising Shot, Rising Blade, Magic Lance, Terra Lance, Aqua Lance, Wind Lance, Fire Lance, Freezing Lance, Lightning Lance, Offensive Sense, Defensive Sense, Force Control.
FAQ
What does Soul Blade do in Cabal Online?
Advanced skill of Blade Aura.
Which class learns Soul Blade?
Soul Blade is learned by Warrior, Blader. It unlocks at class rank 3.
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.