Preparation

Preparation is a rogue skill that when activated, ambush, backstab, circle, 
and bluff will have proc poison blades.  The victim's poison resistance is 
-150 for the purposes of checking whether poison blades is successful.  While 
preparation is active, the user's mana and move regen is 0.

The classes that get the skill preparation are:

rogue      : Level  75 (excellent)