You return to Fortemps Manor to inform Tataru of your plan to attempt a parley with Nidhogg.
Requirements
This quest is available if you have completed the quest Alphinaud's Way.
Starting the Quest
Talk to Alphinaud in The Congregation of Our Knights Most Heavenly in Ishgard to begin the quest.
Return to Fortemps Manor
Go outside and use the nearby Aethernet Shard to go to the Last Vigil Aethernet Shard. Talk to the House Fortemps Guard to enter Fortemps Manor. There will be a cutscene.
Speak with Estinien
Go outside and use the nearby Aethernet Shard to go to the Skysteel Manufactory Aethernet Shard. Talk to Estinien to proceed.
Speak with Redwald
Go west, and go clockwise around the Skysteel Manufactory building until you see a barred gate near Herewart. Go through the gate and continue northwest to reach the Coerthas Western Highlands. Go north to the quest icon on the map and talk to Redwald. There will be a cutscene.
Speak with the Expedition Leader
Go north and cross the Black Iron Bridge, and continue north to where the orange arrow is pointing in the minimap. Talk to the Expedition Leader.
Slay the Beasts
Enter the building and go down the stairs. Dismount and enter the purple circle. Kill the Tamed Polar Bear and the Tamed Warbear.
Speak with the Expedition Leader Again
Go upstairs and outside. Talk to the Expedition Leader to complete the quest.
Next Main Scenario Quest
After you complete the quest, talk to the Expedition Leader to accept the next quest: From One Heretic to Another.