yeah, you have to go down, activate the seed thing, and then follow the campfires to the next one where Robbie should be. Also, watch out for the monsters. They are base teir, but have bad effects when touched.
U mean gloom and u can get rid of it either by eating food with special effects or wear a certain type of armor or staying in a light root or go out in the surface during the day (No Spoilers).