You need 1 Dwarven Spirit, 5 Celandine, and 1 Drowner Brain. If you complete the Twisted Firestarter quest, you'll be able to pick up a Drowner Brain as you go. Otherwise, you'll find these ...

Shortly afterwards you'll learn how to create the Drowner Pheromones potion. You'll need a Puffball, Sewant Mushroom, Dwarven Spirit, Drowner Brain and Sewant Mushroom to craft it.

Make sure you loot the bodies for a Drowner Brain - a handy addition to your alchemy purse. Once killed, continue to follow the footprints into the village and the building, where you'll find Napp ...