You automatically block attacks with a success chance of (5*SkillLV)%. This allows you to Auto Guard melee and ranged attacks with your two-handed sword.
This Skill also enables you to parry the following skills: Bash, Bowling Bash, Pierce, Spiral Pierce, Brandish Spear, Spear Boomerang, Shield Boomerang, Grand Cross, Asura Strike, Soul Breaker, Double Strafing, Arrow Shower and Investigate.
When you block you cannot attack (but unlike Auto Guard, there is no delay). Use this when you get mobbed. Two Hand sword needed

Block an attack using a Two Handed Sword while battling.
When a block is successful, damage from the enemy is canceled, as well as one of the caster's physical attacks.