You vanish into your surroundings with such speed and skill that your enemies can't even begin to guess where you might be.

Daily   ✦     Illusion, Martial
Standard Action      Personal

Effect: When it is not your turn, enemies treat you as invisible if you have cover or concealment from them. An enemy still knows the square you occupy if it saw you in that square at any point during a round. This effect lasts until the end of the encounter or for 5 minutes.

Published in Player's Handbook, page(s) 111.