Asura

Sacrificing his eyes to gain great power, this Slayer strikes a chilling bargain with the demon Kazan to become an Asura. Though blind, an Asura can master magical attacks and defensive techniques, and sharpen skills that utilize waves and long-range weapons. At level 48, an Asura awakens as a Dark Knight.

About Asuras
Asuras are the Slayers who manipulate "waves" and use "the mind's eye". Asuras deal large amounts of damage and can even use elemental waves. GSD is also an asura. (I think GSD is a mix of all subclasses. His demon arm is unbound like soulbender, and he has a bunch of different swords like a weaponmaster. Dont know about the berserker though.)