Once you make it over to the Swamp Forest you’ll encounter an elder in the brickmaker’s village called Vaska (#1). She wants you to clear the area around the Clay Pits (#2) of Drowners and offers a reward of 50 Orens. Head over to the Clay Pits at night and start killing the Drowners.
Once you’ve cleansed all of the pits return to Vaska for your reward. She was lying about the 50 Orens but it’s OK because she gives you the Kezath Sephirah instead which is essential for the next mission.