The Final Maneuver is the final faction quest for the Royal Deadfire Company in Pillars of Eternity II: Deadfire.
Synopsis
The hazanui would like the Watcher's help with something, but she will not give details unless they commit fully to aiding the Royal Deadfire Company.
If the Watcher cements his alliance with her, there will likely be no turning back.
Walkthrough
After you definitively commit to supporting the Royal Deadfire Company, thereby failing all other faction alliance quests, Hazanui Karū tells you what you need to do to gain her support: assassinate Queen Onekaza II in order to allow the Rauatai to take over the archipelago. If at this point you try to back out, the quest fails and everybody in the Brass Citadel turns hostile.
Leave Imperial Command to begin the action. All city districts except Serpent's Crown are now inaccessible, as the Rauataians will be shelling Vailian ships and VTC infrastructure to provide a diversion. Sneak or murder your way through Serpent's Crown and the palace to reach the queen on the palace rooftop. The discussion inevitably concludes with a battle with the queen, her tigers and guards. Among the loot is the queen's Serpent Crown. Alternatively, you can kill Prince Aruihi and report to the hazanui.
Leave the palace and return to the Brass Citadel. KarÅ« then introduces you to your new means of travel: the Blade of TakÅwa, a Rauatai submarine. This completes the quest as well as the overarching main quest The Coming Storm.
TekÄhu won't accept your actions in this quest. He will leave your company, at the beginning of the quest if he is part of the party, or else soon after its completion. In the latter case you can still briefly talk to him in the city, though, and strip him of any valuable equipment. He'll leave you TekÄhu's Farewell. Pallegina will be compelled to return to the Vailian Republics as well, leaving you down two party members.