As far as I understand, when you hit with a weapon that has this ability then your enemy parry is lowered by 10%.
(Similar way like when hitting with bushido spell Lightning Strike you get 50% Hit Chance Increase.)
Parry Damage Property Added: Currently when parried the % is 0, this property will increase that so when you are parried you will still do some damage. Current Cap is 20%
Parry Cap Property Added: This property will lower the parry cap of your opponent only for your attacks with the weapon that has this property. Current Cap is 10%
From the UOE Development Logs 2016
http://uoevolution.com/wiki/index.php/UOE_Development_Logs_2016
