The Witch Swamp in "Stardew Valley" is a very important area in the mountain area of the game. If you want to go to this area, you can first repair the community center, then go to the railway area to trigger the plot, pick up and complete the mage search Return to the Dark Amulet quest.
How to get to the Witch Swamp in Stardew Valley
After repairing the community center, the railway area will trigger the plot. Accept and complete the task of the mage to retrieve the Dark Amulet (after accepting the task, talk to Krobus in the sewer and enter the mutant insect den to find it), and you will be able to enter the northeast corner of the railway area. cave, and reached the Witch Swamp with the help of the teleportation rune.
There is a Goblin blocking the way in the Witch Swamp, and you need to give it Void Mayonnaise (you can get 1 by fishing in the Witch Swamp, only once)