A single-use key that opens four locks across Hallownest. Four exist in the game, four doors need them, and each key vanishes the moment it turns.
The Simple Key is the only single-use key item in Hollow Knight, and there are exactly four of them. Per the wiki, "Simple Keys are items in Hollow Knight. They can be used to open simple locks. Each key can only be used once." Four keys, four locked doors, and zero refunds: every wrong door wastes a slot you cannot recover on that save.
The in-game description reads "simply, a Simple Key. It will fit a variety of locks, which is useful if you like to poke around in places you don't belong." According to the wiki, the four doors are the Royal Waterways entrance in the City of Tears, the locked cave in Dirtmouth (which leads to Confessor Jiji or Steel Soul Jinn), the Pleasure House entrance in the eastern City of Tears, and the Godseeker's cocoon at the bottom of the Junk Pit.
The wiki specifies the four sources: one purchased from Sly in Dirtmouth, one tucked above the City Storerooms in the City of Tears, one on a Royal Retainer corpse in Ancient Basin, and one dropped by the Pale Lurker in the hidden room behind the Colosseum of Fools. Sources and doors line up one-to-one, which means every Simple Key matters for 112% completion.
This guide covers all four Simple Key sources and the prerequisites for each, the full list of locked doors they open, the recommended door order (which key to spend first), the Junk Pit trash-burn warning that catches new players, and the Steel Soul Mode change that swaps Jiji for Jinn behind the Dirtmouth cave.
Simple Key, a single-use key that opens any simple lock.
Four total, one per locked door. No farming, no refunds.
Sly, 950 Geo in Dirtmouth; the only purchasable Simple Key.
Junk Pit trash piles; they consume a key for no reward.Simple Keys are consumables. Per the wiki, "each key can only be used once," and the inventory icon disappears the moment the Knight turns it in a lock. There is no lockpicking alternative, no Charm that bypasses a simple lock, and no way to break a locked door with the Nail.
According to the wiki, the four Simple Keys and the four locked doors line up exactly. The game is balanced so that a 112% run can open every door without leaving a key unused; the inverse is also true, which is why the Junk Pit trash-pile warning matters. Spending a key on the wrong target locks the player out of one of the four destinations on that save.
The wiki specifies that the item icon is internally called the "graveyard key." In the game files, both a "Bath house key" and a "Waterways key" exist as unused sprites, "implying that Jiji/Jinn's cave, the Pleasure House, and the Royal Waterways were each originally planned to be opened by these unique keys." Team Cherry consolidated the three unique keys into a single shared Simple Key during development.
Track Simple Key inventory before every visit to a locked door. Per the wiki, the inventory counter shows the current keys held. In actual play, the cleanest pattern is buying Sly's first (unlocks immediately), grabbing the City Storerooms key after Mantis Claw, then routing Ancient Basin and Pale Lurker as their gates open.
Per the wiki, the four Simple Keys come from four distinct sources scattered across three regions plus Dirtmouth. The table below lists each, the region it sits in, and the gate the Knight has to clear to claim it.
| # | Region | Source | Requirement |
|---|---|---|---|
| 1 | Dirtmouth | Sly's shop | 950 Geo, one-time purchase |
| 2 | City of Tears | Above the City Storerooms | Topmost right alcove of the Winged Sentry room |
| 3 | Ancient Basin | Royal Retainer corpse | Inside a Mawlurk corpse, west of the tram |
| 4 | Behind the Colosseum | Pale Lurker kill (Godmaster) | Hidden room behind the Colosseum of Fools |
The first Simple Key most players see is the one Sly sells in Dirtmouth 
. Per the wiki, "one can be bought from Sly in Dirtmouth for 950 Geo." It is the only purchasable Simple Key in the game, and the stock refreshes once: Sly carries exactly one Simple Key on his shelf and never restocks.
According to the wiki, "one can be found in the City of Tears, in the big room with Winged Sentries and a Whispering Root just below the City Storerooms" 
. "The key is located in the topmost alcove on the right of the room." The pickup needs Mantis Claw for the wall jumps and is usually grabbed during a normal City of Tears sweep.
The wiki specifies that "one can be found in the Ancient Basin 
, on the dead body of a Royal Retainer inside a Mawlurk corpse." The key is a lore-loaded pickup: a White Palace Retainer who fled the Pale King's palace, was swallowed by a Mawlurk, and left the Simple Key behind. The room is reached via the tram from King's Station.
Per the wiki, the fourth Simple Key drops from "killing the Pale Lurker in a hidden area behind the Colosseum of Fools 
." The Pale Lurker is a Godmaster-content mini-boss who hides in a sealed chamber accessed by breaking a hidden wall east of the Colosseum entrance. The fight is short but unforgiving; players without the Godmaster DLC do not have access to this key.
Per the wiki, "there are 4 locations that can be opened using Simple Keys." The table below pairs each door with what sits behind it and the cleanest source to spend on that door.
| Door | Region | What's behind it | Notable reward |
|---|---|---|---|
| Royal Waterways gate | City of Tears (south) | Entire Waterways region | Isma's Tear, Flukemarm, Dung Defender |
| Dirtmouth cave | Dirtmouth (east) | Confessor Jiji (or Jinn) | Shade recovery for Rancid Eggs |
| Pleasure House | City of Tears (east) | Hot Spring + Millibelle | Full-Mask refill spring; 4-floor pickups |
| Godseeker's cocoon | Junk Pit | The Godseeker NPC | Godtuner, Godhome access |
According to the wiki, the Royal Waterways gate sits in the southern City of Tears and "opens the entrance to the Royal Waterways 
from the City of Tears." The Waterways are the densest pickup region in the game: Isma's Tear (acid swim), Flukemarm (Flukenest charm), Dung Defender (White Defender chain), Tuk (Rancid Eggs), and the Defender's Crest charm all sit behind this single Simple Key.
The wiki specifies that the cave on Dirtmouth's east side opens to Confessor Jiji, the Rancid Egg moth who summons the Knight's Shade for free. On Steel Soul Mode, per the wiki, "Steel Soul Jinn replaces Jiji" in the same cave, swapping Shade summoning for Rancid Egg trading. The same Simple Key unlocks whichever NPC the difficulty mode assigns.
Per the wiki, the Pleasure House 
gate is in the eastern City of Tears and opens to the Hot Spring building. The Hot Spring refills full Masks, full Soul, and Lifeblood Masks on contact; the building also houses Millibelle 
the Banker on floor 4. Burning a Simple Key here is a tier-3 quality-of-life unlock.
The wiki specifies that the deepest Simple Key door opens the Godseeker 
cocoon "deep in the Junk Pit , the lowest section of the Royal Waterways." Opening the cocoon hands over the Godtuner 
and unlocks the entire Godmaster DLC pantheon arena.
Spending Simple Keys in the wrong order leaves Geo on the table and slows region unlocks. In practice, the cleanest spend order is: Royal Waterways first, then Pleasure House, then Dirtmouth cave, then Godseeker's cocoon at the very end of the run.
According to the wiki, the four Simple Keys come from four distinct gates, so the recommended order also aligns with the natural ability gate sequence: Sly's key opens immediately, City Storerooms comes after Mantis Claw, Ancient Basin opens after the King's Station tram, and the Pale Lurker is reachable post-Wings.
The Dirtmouth cave changes occupants on Steel Soul Mode. Per the wiki, "Steel Soul Jinn is located on the very east side of Dirtmouth, within a cave that requires a Simple Key to open." Jinn replaces Confessor Jiji because Steel Soul's permadeath makes Jiji's Shade recovery service useless: there is no Shade to recover when death deletes the save.
According to the wiki, Jinn buys Rancid Eggs for 290 to 449 Geo each, with the payout ramping as more Eggs are sold. "She is disgusted by Rancid Eggs, but will still buy them for Geo 290-449 each, as a favor to a friend which she claims appreciates them." The implied friend is Jiji from the standard mode.
The wiki specifies that "Jinn speaks in rhythm and claims to be too young to tell anything about herself beside her purpose of providing and trading. Her metallic body cannot take damage." She is one of the few NPCs the Knight can swing the Nail at without applying damage. The Simple Key opens the same door; the Steel Soul flag swaps which merchant the Knight finds inside.
The Simple Key touches Sly's shop, the Royal Waterways, and the Godseeker's cocoon. These spokes pick up the connected threads.
Game data and screenshots adapted from hollowknight.fandom.com, used under CC BY-SA 3.0. Original content remains the property of the wiki contributors and Team Cherry.