Located between two large sand-banks, this pass of fine sand is the easiest and most obvious way to descend into the valley of the Great Temple. It's also a really useful open alleyway to get camels or a large convoy of supplies (or looted treasure) in or out of the valley as well, with good points for sentries to look out and see potential threats. It's strange that the gnolls active in this area don't use this as a base of operations- to your eyes at least. The gnolls don't use it because they know better.
When passing through the pass and there is more noise then a whisper (people talking, heavy metal armor, loud animals, etc.), there is a chance the pass will be covered in an avalanche of sand. The chance of this happening is a 1 in 10, which increases by +1 in 10 each time you pass thru without it collapsing. Once it collapses; over the next few months the sand will slowly be blown away until the pass can avalanche again- until then it is safe. Anyone buried in the avalanche is presumably dead; but digging here for a while you can recovery anything they were carrying, or in the case of beasts-of-burden, dig them back up for much needed rations.
Some say that the Gods of the Mozz created avalanches of snow and sand- any disaster made by disturbing the earth could not be made by passage on silent wings.