Scarlet Reign's Great Red Sand

Investigate the Scarlet Sand Slate in all three large obelisks in the 3.1 Sumeru Desert. Each obelisk is clearly visible on the map (one is northwest of King Deshret's Mausoleum, one is east of Khemenu Temple, and one is southeast from the Dune of Elusion), but they are usually paired up with a complicated way inside through Sumeru Desert underground hell. Therefore, just use this video for reference.