Glancing blow

A Glancing blow is an additional hit caused with a two-handed weapon. Glancing blows initially have lower chances of hitting and do significantly less damage than ordinary attacks, but they can hit multiple enemies.

Glancing blows are an inherent property of all two-handed weapons, including quarter-staffs. No Feats or Enhancements are required to enable them, though some make them better.

Basic mechanics
One free glancing blow attack is made automatically against all enemies in a wide arc in front of your character on the first and fourth swing (if you have a fourth swing) of your attack sequence. You must be stationary,otherwise if you move while attacking, then you don't get Glancing Blows. It is possible -- in fact, common -- to get both a glancing and a normal attack against your main target. These are rolled separately.

Glancing blow weapon damage, and chance of applying special weapon effects can be increased by the Two-Handed Fighting feat line, by some Fighter enhancements, Barbarian enhancements, Half-Orc, and Warforged enhancements.

Glancing blow attack rolls use all your normal attack modifiers plus a -5 penalty.

Glancing blow weapon damage has a minimum of 1, however Damage Reduction applies against it normally, and can reduce the damage to zero.

Glancing blow weapon damage starts at a base of 20%, and can be increased by the Two-Handed Fighting feat line, and Barbarian enhancements.
 * Two-handed weapon damage glancing blows starts at a base of 20%.
 * The feat Two-Handed Fighting adds 10% weapon damage to glancing blows.
 * The feat Improved Two-Handed Fighting adds 10% weapon damage to glancing blows.
 * The feat Greater Two-Handed Fighting adds 10% weapon damage to glancing blows.
 * The Barbarian capstone Barbarian Might adds 10% weapon damage to glancing blows.

Glancing blows ordinarily do not cause any weapon effects, but will do at some percentage if you take any of the Two-Handed Fighting feat line, Kensai Specified Weapon Mastery I & II, Frenzied Berserker I, II & III, the capstone Barbarian Might, Orcish Great Weapon Aptitude, Warforged Great Weapon Aptitude Enhancements.
 * Two-handed weapon special effects glancing blows start at a base of 0%.
 * The feat Two-Handed Fighting adds 3% chance to produce special weapon effects on glancing blows.
 * The feat Improved Two-Handed Fighting adds 3% chance to produce special weapon effects on glancing blows.
 * The feat Greater Two-Handed Fighting adds 3% chance to produce special weapon effects on glancing blows.
 * The enhancement Greater Two-Handed Fighting adds 3% chance to produce special weapon effects on glancing blows.
 * The enhancement Kensai Specified Weapon Mastery I adds 5% chance to produce special weapon effects on glancing blows.
 * The enhancement Kensai Specified Weapon Mastery II adds 5% chance to produce special weapon effects on glancing blows.
 * The enhancement Frenzied Berserker I adds 2% chance to produce special weapon effects on glancing blows.
 * The enhancement Frenzied Berserker II adds 2% chance to produce special weapon effects on glancing blows.
 * The enhancement Frenzied Berserker III adds 2% chance to produce special weapon effects on glancing blows.
 * The capstone Barbarian Might adds 5% chance to produce special weapon effects on glancing blows.
 * The enhancement Orcish Great Weapon Aptitude I adds 2% chance to produce special weapon effects on glancing blows.
 * The enhancement Orcish Great Weapon Aptitude II adds 2% chance to produce special weapon effects on glancing blows.
 * The enhancement Orcish Great Weapon Aptitude III adds 2% chance to produce special weapon effects on glancing blows.
 * The enhancement Warforged Great Weapon Aptitude I adds 2% chance to produce special weapon effects on glancing blows.
 * The enhancement Warforged Great Weapon Aptitude II adds 2% chance to produce special weapon effects on glancing blows.
 * The enhancement Warforged Great Weapon Aptitude III adds 2% chance to produce special weapon effects on glancing blows.