The Immortal Flames are planning to use Ungust as bait to catch the Amalj'aa kidnappers, and Minfilia asks you to assist.
This quest is available if you have completed the quest Life, Materia and Everything, and have reached level 20.
Starting the Quest
Talk to Minfilia in the Waking Sands in Vesper Bay in Western Thanalan to start the quest.
Report to the Flame Sergeant at Camp Drybone
At Camp Drybone, go into the building east of the Aetheryte and talk to the Flame Sergeant.
Lie in Wait at the Invisible City
Exit the building and go northeast and through the archway, then up the ramp. Go north and fight your way through Vandalous Imps and Rotting Corpses to reach your destination. There will be a glow around the destination, indicating an instanced battle. Check on it and there will be a cutscene, and then the battle will ensue.
Solo Duty: Lord of the Inferno
Kill the Amalj'aa Bruisers first, then the Amalj'aa Rangers. When more Bruisers appear, kill them first, then the Rangers. But if the Amalj'aa Halberdiers are reducing your health too much, kill them before dealing with the others. You can ignore Highcant Hatsugg Chah.
Eventually, the battle will end, and there will be a cutscene.
Speak with the Flame Sergeant
Talk to the Flame Sergeant in the area. This will unlock The Bowl of Embers. Unlike previous duties, this is a trial instead of a dungeon. Trials are single boss battles.
You can leave the area by talking to the Flame Private near the pool of water.
The Bowl of Embers
Use the Duty Finder or Duty Support to enter The Bowl of Embers. Please see the The Bowl of Embers for a walkthrough.
Speak with Thancred
After you defeat Ifrit, you will be back in Camp Drybone. Talk to Thancred east of the Camp Drybone Aetheryte.
Report to the Scion
Use a Vesper Bay Aetheryte Ticket (which you received after completing the quest The Scions of the Seventh Dawn) to return to Vesper Bay. Go into the Waking Sands and talk to the Scion of the Seventh dawn. There will be a cutscene.
Next Main Scenario Quest
After you complete the quest, talk to Minfilia to accept the next quest: A Hero in the Making. There will be a cutscene.