Desert Scar is one of the locations which needs to be finished when completing the tasks from Virides the Rogue in the Vault of Guardians. The goal in this location (as well as the others in this particular quest) is to obtain a mask from the pedestal.
BUT, to get the mask you need to get the keys! So where to look for them?
To be able to reach the mask, you need to activate three bridges. The main bridge leading to the mask can only be activated by the two blue light beams which need to be directed to the receivers next to the pedestals. And here's the tricky part: to direct the beams, Diggy needs two mirrors as well. Each one is located on a separate isle and to get there, you need to activate two more bridges. These can only be opened with the levers next to the entrance. The levers will work only when you have the Triangle keys.
Please check the skeletons lying on the ground throughout the location. Once you click on them, a ghost will try to scare you, but then a precious key will pop out. Now you're good to go, find one more, use them to activate the lever and claim the mask!