Additional Effect

The term "Additional Effect" is placed on certain attributes of a Weapon, Armor, or Ammunition that have a percentage chance of activating, usually while in combat. The frequency of the Additional Effect's activation, or proc rate, is based on many factors, the most common of which are the weapon and the level of the mob being attacked. However, it is generally not a good idea to rely on the Additional Effect of a weapon, as even the best non-relic Additional Effects proc fairly infrequently.