As The Tyrant rose to power, some anticipated the Ashfall and built defences to protect themselves and their treasures. When the ash came, it killed them, buried them, and corrupted them into undead. Now buried under The Ash, a vast desert of sand and ash and is said to likely contain Orikal, a metal most receptive to magical enchantment in a metal-starved setting. And Theadirea was famous for her arcane knowledge. Many treasures might lie in her Vault! (5e setting version)