I'm not sure where to add this into the page for The Assassin, so I'll put it here for now:
Voyage name: Honing her Craft.
Description: The Assassin thinks there's a chance to practice her craft at a garrison, on the Rapa Causeway, by thinning the number of mercenaries and bounty hunters there. Help the Assassin practice her craft.
Rewards: 10,000 experience.
The outcome (the cutscene, showing the voyage was successful) I got from doing this special voyage was that Ling was betrayed by her source (Kurai?), was ambushed and did not kill Baby Tooth, and so she was going after Kurai next.