Stardew Valley Sewer Key: 60 Museum Donations Unlock It

What the Rusty Key actually unlocks

The sewer grate under Pelican Town only opens once you hold the Rusty Key, and the Rusty Key only arrives when the Museum has seen 60 donations. That single gate makes the sewer the one part of the valley locked behind the museum rather than behind a skill, a season or a season pass — which is why many players reach year two without ever setting foot in it.

Once inside you meet Krobus, the shadow person who can later move in as your roommate; the Statue Of Uncertainty, which rebuilds a profession for gold; and the doorway into the questline that ends at the Witch's Hut. All of it begins with the same pile of rocks, minerals and dug-up artefacts.

The 60-donation rule, in numbers

Museum donations count two kinds of item: minerals and artifacts. Gunther takes each one only once, and it is the running total — not the mix — that triggers the rewards. The museum has 102 display spaces, but only 95 items in the whole game can ever fill them, so "100% complete" is really 95 items, not 102.

The Rusty Key sits at 60 of 95 donations, which is 63.2% of the collection. That leaves 35 items still to find before the museum is finished, and by long experience those last 35 — usually a clutch of rare artifacts — are what stretch the grind out. The threshold is a raw count, so a stack of common geodes gets you there exactly as fast as a lucky rare-find; duplication, not rarity, is what slows you down.

The earlier milestones are worth knowing because several hand you things you would otherwise buy; Gunther mails each reward the morning after you cross its threshold.

There is a second track for minerals alone. Hand Gunther 50 minerals and he rewards you with a Crystalarium — the single most valuable museum reward in the game, because a Crystalarium duplicates any gem you feed it, every day, forever. If you only chase one museum milestone beyond the Rusty Key, chase that one.

Three worked examples

Every number below is worked in the script that builds this page, from the counts above.

Example 1 — reaching 60 donations

You need 60 donations out of 95 possible, and there are 53 minerals and 42 artifacts to choose from. Two clean routes both land exactly on the threshold:

• Minerals first: donate all 53 minerals, then 60 − 53 = 7 artifacts. This is the fast route — minerals come from ordinary geodes, which you crack by the dozen in the mines.
• Artifacts first: donate all 42 artifacts, then 60 − 42 = 18 minerals. Slower, because artifacts need digging and fishing.

Either way 60 ÷ 95 = 63.2% of the collection is the price of entry, and 35 items remain for the full-completion Stardrop.

Example 2 — the friendship curve to a Krobus roommate

Krobus will only sell you the Void Ghost Pendant — the item that invites him to move in — once you have 10 hearts with him, and each heart costs 250 friendship points. That is 10 × 250 = 2,500 points to qualify.

A steady weekly routine adds: talking every day (20 × 7 = 140) plus two loved gifts a week (80 × 2 = 160), for 300 points per week. At 300 ÷ 250 = 1.2 hearts a week, the 2,500 points take 2,500 ÷ 300 = 8.3 weeks, or about 59 days.

The shortcut is his birthday on Winter 1, when a loved gift is multiplied eightfold: 80 × 8 = 640 points in one morning. Krobus's loved gifts are cheap once the mines are open — a Void Egg or a Diamond both qualify, and he pays for his own Void Eggs from his own shop.

Example 3 — the sewer's gold maths

Two costs define the sewer economy. The Statue Of Uncertainty changes one profession per use for 10,000g, and Krobus sells Void Essence at 100g each. Priced in the currency the shadow economy already uses, one reroll is 10,000 ÷ 100 = 100 Void Essence, and three rerolls in a session cost 30,000g.

The shop's big ticket sits at the other end. Krobus's single Stardrop costs 20,000g — the equivalent of 2 profession rerolls — while the Return Scepter at 2,000,000g is 200 rerolls on its own. The Void Ghost Pendant you need for the roommate path is bought with goods rather than gold: 200 Void Essence from the Desert Trader, which at Krobus's own price is about 20,000g of value — and the pendant itself sells for 4,500g if you change your mind.

The Dark Talisman chain, step by step

The sewer is the door to the Witch's questline, but the chain only opens after the Community Center bundle or the Joja Community Development Form is finished. The order matters, because two of the steps are easy to do out of sequence and get stuck on.

• Trigger it at the Railroad. With the Community Center (or Joja route) complete, walking into the Railroad area plays a cutscene in which the Wizard asks for his stolen magic ink.
• Talk to Krobus. He is the one who knows where the ink went — and, more usefully, he opens a passage inside the sewer to the Mutant Bug Lair, where the Dark Talisman waits in a chest.
• Take the Talisman back to the Railroad. Place it on the artifact blocking the cave mouth; the way to the Witch's Swamp opens and a teleportation rune appears.
• Deal with the Goblin. The Witch's henchman blocks the path to the hut and only steps aside for a Void Mayonnaise, which also completes the quest "Goblin Problem".
• Fetch the Magic Ink and return. The ink sits on a table inside the Witch's Hut; hand it to the Wizard and he unlocks the advanced magic buildings for your farm.

Returning the ink unlocks six wizard buildings for the farm and three dark shrines in the hut, and it gives you a permanent teleport link between the hut and the Wizard's Tower basement once you have four hearts with the Wizard. Before that fourth heart you can travel from the hut to the basement but not back, which catches out a first-time visitor with no farm return.

Krobus as a roommate

Krobus is the only character who can move in without romance. Once you hold 10 hearts and are unmarried, buy the Void Ghost Pendant from the Desert Trader for 200 Void Essence and give it to him; he moves in three days later and adds a room beside yours.

He is not a spouse — no children, no wedding — but he behaves like one in every way that matters mechanically. He keeps your farm tidy, he can be gifted as normal, and at 13 hearts he hands over a Stardrop, the permanent energy upgrade, exactly as a spouse would. If you have already married someone else the pendant becomes impossible to get, so plan the roommate path before any engagement.

What else is down there

The sewers are more than a doorway. The Statue Of Uncertainty is the only way to change a profession after you have picked it — pay it 10,000g, choose one skill, sleep, and you re-answer that skill's level 5 and level 10 profession prompts overnight. Two details trip players up: only skills where you have already chosen a profession appear in the menu, and the old profession's bonuses stop as soon as you select it, so any shipped items in the bin that day miss the old bonus.

The sewer water is also a fishing spot: the Mutant Carp, one of the game's legendary fish, and the Radioactive Carp of the legendary-fish-II set live here, and the Slimejack sits in the Mutant Bug Lair reached through Krobus.

Where players get stuck

• Assuming the donation mix matters. It does not — only the running total does. 60 of 95 is the bar.
• Forgetting you can't pick up an item you already donated. Duplicates are wasted; sell or keep the spare and donate the first copy.
• Rerolling a profession the day you ship a big haul. The bonus drops the moment you choose the change, and the shipping bin is settled that night — move the goods first, or accept the loss.
• Crossing the sewer threshold without a Void Mayonnaise ready. The Goblin will not budge, and the quest stalls until you have one. Craft it from a Void Egg in a Mayonnaise Machine before you travel.
• Entering the Witch's Hut with four fewer hearts than you thought. Below four Wizard hearts you can jump to his basement but not return, stranding the trip.

Sources and standards

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