Causes your attacks to ignore X% of your target's Armor and increases the damage dealt by your Rupture ability by Y%.
Serrated Blades is a 10 point talent in the Subtlety for Rogues. It was introduced in Patch 1.10 as a replacement for improved Rupture, and is a strict improvement over that talent. It is the pre-requisite for the 20 point talent Hemorrhage.
Serrated Blades is a passive ability that increases the rogue's damage output by allowing the rogue's attacks to ignore a small percentage of the target's armor. Also increases the damage of Rupture.
Patch 3.3.3 (2010-03-23): This talent now allows the rogue to ignore up to 3/6/9% of the target's armor, rather than a fixed amount of armor ignored per level of the rogue.
Edit
Patch 3.3.3 (2010-03-23): This talent now allows the rogue to ignore up to 3/6/9% of the target's armor, rather than a fixed amount of armor ignored per level of the rogue. 
