From Pathfinder Advanced Player's Guide, which isn't enabled.

Eldritch Debilitations

FEAT 10

Prerequisites eldritch trickster racket; Debilitating Strike

You know how to apply debilitations that are particularly troublesome for spellcasters. Add the following debilitations to the list you can choose from when you use Debilitating Strike.

Debilitation The target is Stupefied 1.
Debilitation The target can't Step.

Pathfinder Advanced Player's GuideOGL