You raise a roiling curtain of airborne dust about a foot thick. Living creatures passing through the wall must make a successful Fortitude save or be blinded for 1 round. The wall is semisolid and does not block line of sight or line of effect, but provides soft cover (+4 AC) to anyone behind it. The squares containing the wall are difficult terrain (each square moved counts as two squares of movement, with each diagonal counting as three squares). The wall must always stand on the ground, and you can make it twice as long by making it half as high (10 ft./level long and 5 ft. high). As a move action, you can direct it to move along the ground at up to 20 feet each round.