Blend Into Shadows( Drow of the Underdark, p. 47)
You can draw from nearby magical shadow to cloak yourself in darkness.
Darkness as a spell-like ability,
As a swift action, you can spend a use of your darkness spell-like ability to make a Hide check, even while being observed and without cover or concealment. You must be within 10 feet of an area of magical darkness.
You also gain one additional daily use of your darkness spell-like ability.