How to complete the Laundanum quest in Valor Mortis

Finding Laudanum in Valor Mortis is the focus of the titular quest, and it's not easily done. If you've been working your way through The Outskirts chapter of Valor Mortis, you've probably been using the Island of Whispers lantern quite frequently, as the area loops back to it multiple times. While opening the final shortcut, you've also probably been summoned to speak with an old lady by a door who has asked you to find a bottle of Laudanum for a side quest by the same name. Lucky for you, we k