Dragonflight Dungeon Event returns with the weekly reset. Completing four Mythic difficulty or higher Dungeons rewards a piece of Heroic Vault of the Incarnates loot.
When you log in this week, make sure to pick up the Emissary of War quest, which requires you to complete four Mythic Dungeons (either Dragonflight Mythic 0 or any Keystone dungeon) to receive a Cache of Vault Treasures.