The Skull Key is one of the few items in Stardew Valley that you would consider an end-game item. As well as being extremely hard to find, it unlocks a beautiful mine once you have it. Luckily, we have written about where to get it and what to do with it.
Where can I find the Skull Key in Stardew Valley?
You can obtain the Skull Key by reaching the bottom of The Mines at the 120th level and opening the chest with the Skull Key inside.
It will take days to get through this chore because you'll lose energy with each outing. You should spend your time unlocking checkpoints to start each trip closer to 120.
Make sure you have a pickaxe that you can upgrade and food that you can eat to regain health and energy. Once you've obtained the Skull Key, you'll get the message, "you found a strange-looking key in the bottom of The Mines."
Now, you must use the Skull Key to unlock the next adventure.
What is the Skull Key used for in Stardew Valley?
The Skull Key is used to unlock Skull Cavern. Skull Cavern is found on the north side of the Calico Desert and is a high-difficulty Mine with an unlimited amount of levels to explore.
You can only access calico Desert by purchasing the Vault Bundles at the Community Center or purchasing the Bus Development from JojaMart for 40,000 gold. You can then take the bus for 500 gold.
For more on Stardew Valley, check out Does Stardew Valley have cross-play? or How to Play Stardew Valley Co-op Online and Splitscreen here on Pro Game Guides!