Into Udam Land
Go into Sayla's hut to start a cutscene. She speaks about screams and wishes you could stop them but the way to the Udam land is blocked by rot fumes.
She says she knows how to make an antidote and needs some ingredients. Go to the place indicated in the map.
You will find an odd-looking stone structure that seems to be sheltering the herbs you are looking for.
Just as you are picking the roots, some Udam show up along with Ull, and knock you out.
You wake up in prison and receive some choice words from Ull.
Your next task is to escape your cell. Follow the tracks that are marked in red. Grab the conveniently placed Grappling Hook and get out of the cell.
Next, retrieve the gear they have confiscated. It is along the tracks and being tampered by an Udam. Say hi to him.
Continue following the tracks. Note that if you do not have cold protection, remember to watch your cold meter. You can also find some Udam who seem to be "shivering" it could be because of the Skull Fire or.. they are just cold. Probably the latter. So help keep them warm by setting their bed on fire. Good Takkar.
Eventually, you will reach a cavern with some enemies. Dispose of them and continue following the tracks.
You will again find another cavern with more enemies. Dispose of them again. (You can find more "cold" Udam. Warm them up ;)
Here, you will find yourself in the last cavern. You will be tasked to kill the Cave Guardian. He is up there, in the center doing some... "business".
You can take him out instantly if you have the Shard Takedown skill by sneaking up into the cheering Udam behind him and throwing a shard his way.
Kill the rest of the enemies and continue following the tracks to the exit to complete the mission.
You will automatically go back to Sayla and she will teach you the recipe.