The Painted Masks

 is a quest in.

Synopsis
Aloth has spent the last five years trying to deal with the Leaden Key, but the task has proven difficult. He wants the Watcher's help to find a Leaden Key cabal in Deadfire that may provide him with much-needed insight. He said no one in the region seems to know that name, so our best hope is to keep an eye out for signs of the Leaden Key.

Walkthrough
After Act 2 and once your reputation with Aloth reaches 1, he will talk to you and ask for help with finding the cabal. **Aloth will choose whichever trait is higher. See the dialogue table below.
 * Head northwest, into Rikuhu's Maw, and sail around waiting for an encounter with a deserted ship. Its sails will bear a variant of the Key's insignia.
 * Board the ship. Investigate the soul to learn that a Huana tribe has attacked the ship, abandoning it dead in the water.
 * Talk to Aloth. He will reveal that he has also found stains, which you can identify as koiki pulp with Survival 4. With History 7 you can determine their relation to Wahaki hunters.
 * Continue to Ori o Koīki. Aloth will notice a mural displaying Thaos in the Wahaki shrine.
 * Talk to the ranga, Ruāsare, and mention Thaos and the Leaden Key. This will allow you to read her soul (read the full memory below).
 * The memory shows Ruāsare's past life as a long-ago chieftain of the Wahaki. Thaos came to scare her people into abandoning the Engwithan ruins. She executed Thaos instead, yet their interaction cemented the Wahaki's suspicion of outsiders. Thus, the tribe has unintentionally served the Leaden Key's interests for almost two thousand years by protecting the ruins.
 * Speak with Aloth about the memory. How you answer his question, "Might I be to blame?", determines his end-game slides. Aloth will either feel responsible for the consequences of his actions and decides to drop his pursuit, or feels absolved and continues his Leaden Key work.

He can either be heartened by knowing that even Thaos' imperfect efforts have progressed his grand schemes (which grants him Adaptive), or think that his approach truly doesn't matter (which grants him Persistent).

Absolved/Responsible dialogue
These conversations will influence his feelings of absolution or responsibility. If you let Aloth decide at the end of the quest (or don't finish the quest), whichever of these traits is higher will dictate his end-game slides.

Ruāsare's memory
You will move hundreds of generations back, to the memory of a strange, foreign man:

Trivia

 * Note that killing the ranga for the quest Tip of the Spear will cause her soul to exit her body and linger above her corpse so that you may interact with it, thus preventing the quest from being stuck.