Face to face with the daemon in search GREENHALL, You will venture deeply into a dangerous marsh to try to find a demon whose witness you have witnessed in a vision. When you arrive for the first time in the marsh, you will talk to a hermit that will talk about a group of people who have tried to explore the region.

Go to the mission marker in the marsh, then explore each zone highlighted. Make sure to explore thoroughly because you want to find two objects in chests at one of the locations. This is only part of a log entry and a demonic potion. You will need both to finish this quest. When you have completely explored all marked areas, come back to the old man. He will answer various questions, then ask you to go playing the battery.

You have to go to the center and find the drums. Remember that it is crucial to play only every drum once, otherwise the sequence breaks, and you will have to fight against some monsters before you can try again.

You want to play the battery in the following order

Yellow insect
Red snake

Greedfall Beat the Drums, Find Rusty Chest Key & Acquire the Potion (Face to Face with the Demon )

Then you will pass to the next part of the quest. I will not leave spoilers here for you, but have fun.