Glancing blow

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

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

As of Update 5, two exotic weapons - bastard swords and dwarven waraxes cause glancing blows when wielded alone or with a shield (or with a Rune Arm, which Imbues each glancing blow with extra damage as well), not when used in two-weapon fighting. Despite being one-handed weapons, these glancing blows are improved in the same manner as two-handed weapons, including the Two Handed Fighting feats and class enhancements.

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. If you move while attacking, you don't get glancing blows. As of Update 23, Glancing Blows now work while moving if a character has the Two Handed Fighting feat. 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 certain enhancements available to Fighters, Barbarians, Half-Orcs, and Warforged, and by the Epic Destiny Fury of the Wild.

Glancing blow attack rolls use your normal attack modifiers with 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.

Damage
Glancing blow weapon damage starts at a base of 20% of a regular hit. Feats and enhancements increase the damage.
 * Two-handed weapon damage glancing blows starts at a base of 20%.
 * The feat Two-Handed Fighting adds 10%, for a total of 30%.
 * The feat Improved Two-Handed Fighting adds 10%, for a total of 40%.
 * The feat Greater Two-Handed Fighting adds 10%, for a total of 50%. Additionally, it grants a glancing blow on your third attack while standing.
 * The Barbarian capstone Barbarian Might adds 10% weapon damage to glancing blows.

Weapon special effects
Glancing blows ordinarily do not cause any special weapon effects. Feats and enhancements can change this.
 * 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 Kensei Specified Weapon Mastery I adds an increased chance to produce special weapon effects on glancing blows.
 * The enhancement Kensei Specified Weapon Mastery II adds an additional increase 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 enhancement Great Weapon Aptitude adds 2%/4%/6% chance to produce special weapon effects on glancing blows.