Scorpion's Instincts( Sandstorm, p. 53)
You are hard to find in the waste.
Hide 5 ranks, DEX 13,
You have an inborn sense of where to lurk without being seen, gaining a +2 bonus on your Hide checks and reducing the distance within which creatures can detect you by scent to 10 feet (20 feet if upwind, 5 feet if downwind). If you are in an area covered in a layer of at least 1 inch of ash, dust, loose earth, or sand, you gain an additional +2 bonus on Hide checks, a +2 bonus on Move Silently checks, and a creature can detect you by scent only if it is within 5 feet (pinpointing your location as normal).