Desert Temple - Shift Sands

From the introduction:

A long day out from the main town in the heat of the desert lands, you and your group are travelling along on the back of a gigantic lizard. As you look ahead, you see strange bumps in the sands—flowing across the sands as if it were water. At first glance, they seemed like sand sharks, but then scorpion tails surface and glide amongst the sand—circling about the lizard’s feet. A larger bump comes careening towards you, and a huge scorpion jumps out from underneath the red hot sands and surprises the lizard—forcing you all off of it and onto the sands below.