It can ignore defence bonuses provided by armor (so like the hides of the Black Dragons, or Scales of Metal Dragons), so when the special hits, when determining your chance to hit, the armor of the opponent is treated as not there. HOWEVER it does NOT ignore the Defence LEVEL of the target, so if the inherent defence level of the target is very high, you wont hit much more with verac's set. For example, against a level 70 def with torags, you will find that you will hit more with veracs then for example whip (because verac's armor ignores Torags armor) however it will not increase the chance to hit a naked lv 70 def guy than with something with similar attack bonus as the flail, such as the whip.