The City Lost to Time

 is a quest in.

Synopsis
The game's final story quest and endgame. The relatively short quest sees the Watcher travel to Ukaizo, fight its mechanical guardian, and confront Eothas as he prepares to finally break the Wheel.

Walkthrough
Sailing to Ukaizo
 * Use your best ship, or the one you received in your faction alliance quest, to finally sail to Ukaizo. Fire giant longships will attempt to intercept you. When at you arrive at the opening in Magran's Teeth in the northeast of the map, the game will warn you that you are arriving at the point of no return: you cannot go back to exploring the archipelago after this event.
 * In the following scripted event, you can either join the battle between your allies and their rival faction, or venture into the storm.
 * If you liberated Scyorielaphas, he'll help you out here by fighting off a guardian monster.
 * If you used the Rauataian submarine, you'll approach Ukaizo without further problems.

Ukaizo Harbor
 * As soon as you venture into Ukaizo Harbor, a dragonlike construct, the Guardian of Ukaizo, intercepts you. It's surprisingly talkative, but you'll have to fight it (unless Scyorielaphas has already destroyed it).
 * The Guardian initially summons several Adra Animats, then two Engwithan Sentinels, and finally two Engwithan Hierarchs who can Dominate your team (preventable by eating a Captain's Banquet beforehand). As the fight progresses, the Guardian will gain two additional heads and regenerate.
 * As always in boss fights, it is advisable to use your tank (a character built for defense) to occupy the Guardian, and the others to kill his henchmen and then damage the Guardian. This is the game's final boss fight, so don't hold back on your consumables (but rest up afterwards if you're wounded, as there is one last, lesser fight coming up).

Grand Promenade and Ondra's Spire
 * The next area accessible to you is the Grand Promenade. There's nothing of importance here except a spot in which to talk to your companions one last time. Go on to Ondra's Spire.
 * Atop the spire, shut down the machine to trigger another conversation with the gods.
 * Return to the Grand Promenade to see that one of the factions has braved the storms and caught up with you and won't listen to reason. The circumstances that dictate who this faction will be are more complicated than your reputation score. For instance, favoring one faction over the others and completing all of their faction quests, but then refusing to help them take Ukaizo and going it alone may cause that faction to follow. There is currently no definitive list of what circumstances result in which faction following you to Ukaizo. However, no matter who ends up at the island after you, there will be no negotiating. Put them down. Compared to the Guardian, they shouldn't pose any challenge at all. Proceed to Mói Gweath.

Mói Gweath
 * As you face Eothas one last time in a conversation, the quest concludes, together with the game. You bear witness to Eothas's shattering of the Wheel, and to its consequences.
 * Each of your companions will have their own questions for Eothas. If you've completed the Beast of Winter (DLC) and chose to have Waidwen follow in your trail of souls, he too will appear and have a short conversation with Eothas.