Great-Weapon Grandmaster

Your training putting the weight of a weapon to your advantage has reached the ultimate level. Having complete mastery over letting your weapon’s momentum empower your strikes, you gain the following benefits:

• You can use two-weapon weapons with one hand. 
• You can use two-weapon fighting even when the two-handed melee weapons you are wielding are two-handed.
• Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a - 10 penalty to the attack roll. If the attack hits, you add +20 to the attack’s damage.