How to Get the Rusty Key in Stardew Valley and Unlock the Sewers (Krobus Shop Guide)

Sooner or later, every Stardew Valley player tries to open one of the locked sewer covers around town and gets turned away. Behind them is one of the valley's strangest corners: a dripping tunnel system with a legendary fish, a statue that lets you rewrite your skills, and a shy shadow creature running the best rare-goods shop in the game.

The key to all of it is the Rusty Key, and the only way to get it is to become the Museum's best donor. Here's how to earn it fast, where both entrances are, and what's worth buying once you're inside. This guide is written for Stardew Valley 1.6.

Requirements at a glance

Step 1: Fill the Museum to 60 donations

Gunther, the curator at the Museum and library next to the Blacksmith, accepts any artifact or mineral you haven't donated before. Duplicates don't count, so the 60 must be different items.

1. Donate everything new as soon as you find it. A good habit is to walk past the Museum on the way home from the Mines.
2. Crack geodes at Clint's. Geodes, Frozen Geodes, Magma Geodes and Omni Geodes are the fastest way to pile up unique minerals. Bring several at once.
3. Dig artifact spots. The wiggling worms that pop out of the ground in town, on the farm and on the beach drop artifacts. Hoe them whenever you see them.
4. Mine all the gem nodes in the Mines. Quartz, Amethyst, Topaz and friends all count toward the total.
5. Keep count. Every new item takes a spot on the Museum shelves, so the filled displays are a quick visual check on how close you are.

Once your 60th unique donation is in place, go to bed. The next morning, Gunther meets you at your front door, thanks you for your contributions and hands over the Rusty Key.

In 1.6, the key no longer sits in a wallet. You'll find it in the new Special Items & Powers tab of your player menu. You don't have to equip or use it. The sewer entrances simply open for you from then on.

Step 2: Find a sewer entrance

There are two ways in, and both lead to the same place.

Pelican Town. Head to the southern part of town near Mayor Lewis's Manor and the graveyard. Look for a small fenced-off patch with a square metal cover in the middle. Interact with the cover to climb down.

Cindersap Forest. From Marnie's Ranch, walk south until you hit the river. Cross the wooden bridge, which hops over a small island to the far bank, and keep going south. You'll find a sewer grate with a staircase leading down.

If you try either one before you have the key, the game simply tells you that you can't go in yet.

What's inside the Sewers

Krobus and his shop

The big reason to come down here is Krobus, a gentle shadow person who keeps to himself on the right side of the Sewers. His shop is the only reliable place to buy several rare items:

On top of that, he stocks one extra item that changes with the day of the week. The Friday item is an Iridium Sprinkler for 10,000g, a bargain early on, so it's worth planning a trip around.

The Stardrop should be your first purchase. Each Stardrop permanently raises your maximum energy, and this is one of the few you can simply buy. The Void Egg is the other early pick: put it in an incubator in your Coop to hatch a Void Chicken, which lays Void Eggs of its own.

Befriending Krobus

Krobus is a full friendship character. Two gifts a week are allowed, and he loves Void Eggs, Diamonds, Iridium Bars, Pumpkins and Wild Horseradish, plus the universal loves. At high friendship, you can give him a Void Ghost Pendant to invite him to live on your farm as a roommate. You'll need an upgraded farmhouse so he has his own room. He won't do chores like a spouse, and once he moves in, a chest in the Sewers takes his place as the shop counter.

The Statue of Uncertainty

Regret a profession pick, like Fisher over Trapper? For 10,000g, this statue lets you change the professions for one skill. Pick the skill, pay and go to bed. That night you choose your level 5 and level 10 professions again. Your old bonuses disappear as soon as you confirm the change, so don't do it on a day you're shipping a big batch of goods that depends on them.

Mutant Carp

The Sewers are home to the Mutant Carp, one of the five Legendary Fish. Season, weather and time of day don't matter for it, but it's a hard fish to land. Bring your best rod and bait before you try.

The Mutant Bug Lair

In the upper left, a channel of green water marks a passage to the Mutant Bug Lair. It stays sealed until the Dark Talisman quest, when Krobus opens it so you can retrieve the talisman.

Common mistakes

• Donating duplicates in your head. Only unique items count toward 60. A second Quartz does nothing.
• Waiting by the Museum for the key. Gunther delivers it at your house the morning after your 60th donation, not at the counter.
• Skipping the Stardrop. It's a one-time purchase, but it doesn't expire. Buy it the moment you have 20,000g to spare.
• Changing professions on shipping day. Profession sell bonuses don't apply to items you ship on the day you change.

Quick recap

Donate 60 unique artifacts and minerals to Gunther, then sleep. Collect the Rusty Key at your door the next morning. Enter through the fenced cover in southern Pelican Town or the grate south of the river in Cindersap Forest. Buy Krobus's Stardrop and a Void Egg, catch the Mutant Carp, and keep the Statue of Uncertainty in mind for when you want a different build.