In the sprawling, interconnected world of Hallownest, progress is often barred not by strength alone, but by the lack of a specific, rusted piece of metal. Among the various curiosities you will collect on your journey, the Simple Key is perhaps one of the most vital yet understated items. These keys are single-use tools designed to unlock specific "simple" locks scattered across the kingdom. While the name suggests something mundane, what lies behind these doors ranges from essential gameplay mechanics to massive endgame expansions.

There are exactly four Simple Keys in the base game of Hollow Knight. Because they are consumed upon use, players must track down all four to experience everything the game has to offer. This guide provides a granular breakdown of where these keys are hidden, the challenges involved in obtaining them, and a strategic overview of where to spend them first.

Understanding the Simple Key Mechanism

Before diving into the locations, it is important to clarify how these items function. Unlike the City Crest or the King's Brand, which act as permanent progression markers, a Simple Key is a consumable resource. Once you interact with a compatible lock and confirm its use, the key vanishes from your inventory forever.

The locks they open are visually distinct—typically small, ornate iron hatches or doors that prompt a specific dialogue box. Because there are four keys and four locks, you cannot "waste" a key in the long run, but your choice of which door to open first can significantly impact your early-to-mid-game experience.

Location 1: Sly’s Shop in Dirtmouth

The first Simple Key most players encounter is found right in the fading village of Dirtmouth. However, it isn't just lying on the ground; it must be purchased from Sly, the diminutive shopkeeper.

How to Unlock Sly’s Inventory

You cannot buy the key immediately upon arriving in Dirtmouth. First, you must rescue Sly from his stupor in the Forgotten Crossroads. He is located in a small house near the bottom-right of the area where the Gruz Mother boss resides. After speaking to him and clearing the area, he will return to Dirtmouth and open his shop in the house to the left of the town's central well.

The Cost of Convenience

Sly sells the Simple Key for 950 Geo. For a new player, this is a significant sum. In the early game, you may find yourself debating between this key, the Lumafly Lantern, or various Charms.

Pro Tip: If you are struggling to gather the Geo, focus on exploring the Greenpath or the Fungal Wastes first. Returning to Sly once you have the Gathering Swarm charm will make collecting the necessary funds much less tedious.

Location 2: The Hidden Alcove of the City of Tears

The second key is tucked away in the rain-drenched heart of the kingdom: the City of Tears. This key is often missed because it is located in a transitional room that many players rush through.

Detailed Navigation Route

To find this key, start from the City Storerooms Stag Station. Head downwards and to the right, entering the large, vertical chamber that connects the upper city to the lower sections. This room is filled with Winged Sentries and Heavy Sentries, making it a dangerous place for the unprepared.

As you descend, look for a series of platforms on the right side of the room. Near the top-right alcove, just below the ceiling of this specific section, you will see a glowing item pickup. You will need to utilize basic wall-jumping (Mantis Claw) to reach the wooden scaffolding.

Tactical Considerations

The Winged Sentries in this room can be aggressive. If you have the Vengeful Spirit or Soul Catch charm, it is best to clear the air before attempting the platforming. Once you reach the alcove, you will find the Simple Key sitting on a ledge, guarded by the atmosphere of the weeping city.

Location 3: The Mawlurk Corpse in Ancient Basin

The third key requires a journey into the depths of the Ancient Basin, a desolate area located beneath the Royal Waterways and the City of Tears. This is one of the more atmospheric and slightly disturbing finds in the game.

Reaching the Ancient Basin

You typically access the Ancient Basin by taking the long elevator down from the City of Tears or by dropping through the broken floor in the Royal Waterways. Once you reach the Basin, head towards the west (left) side of the map, past the area where the tram sits.

Entering the Mawlurk

In a large sub-chamber filled with Lesser Mawlurks—creatures that spit orange infection blobs in an arc—you will find the massive, hollowed-out corpse of a Mawlurk. This isn't just a piece of scenery; you can actually walk inside the gaping maw of the beast. Deep within the entrails of the dead creature lies the body of a Royal Retainer. Inspecting the retainer’s corpse will grant you the third Simple Key.

Note: The Mawlurks in this area do not move, but their projectiles deal significant damage. Use the Shade Cloak (if you have it) to dash through the blobs, or simply time your jumps to enter the corpse safely.

Location 4: The Pale Lurker’s Secret Stash

The fourth and final Simple Key was added in the Godmaster content update. It is located behind the Colosseum of Fools in the Kingdom’s Edge and is the only key that requires a mini-boss fight to obtain.

Finding the Hidden Path

Go to the Colosseum of Fools. Instead of entering the main arena, head to the right of the bench area. There is a breakable wall (or a hidden ceiling path, depending on your approach) that leads to the exterior of the Colosseum, overlooking the ash-covered cliffs of Kingdom’s Edge.

The Pale Lurker Fight

In this secluded area, you will encounter the Pale Lurker, a frantic, skittering creature that was once a champion of the arena. She will not fight you head-on; instead, she will run away, dropping spiked traps and firing projectiles behind her.

You must chase her through the looping paths of her lair, dealing damage whenever she pauses. Once defeated, she will drop the final Simple Key. This encounter tests your movement speed and reaction time more than your raw damage output.

Where to Use the Simple Keys: The Four Locks

Now that you have your keys (or know where to get them), you must decide where to use them. Each location provides a unique utility.

1. Confessor Jiji’s Cave (Dirtmouth)

Located at the far right of Dirtmouth, past the graveyard, is a stone door with a simple lock. Opening this door introduces you to Confessor Jiji.

  • The Service: Jiji offers to summon your "Shade" from wherever you last died in exchange for a Rancid Egg. This is incredibly useful if you died in a high-stakes area (like a boss room or a difficult platforming section) and don't want to risk losing thousands of Geo by trying to walk back there.
  • Steel Soul Mode Variation: If you are playing in Steel Soul mode (where death is permanent), Jiji is replaced by Steel Soul Jinn. Since there are no Shades in this mode, Jinn will instead buy your Rancid Eggs for large amounts of Geo, turning a useless item into a lucrative revenue stream.

2. The Royal Waterways Hatch (City of Tears)

In the lower section of the City of Tears, near the center of the map (west of the Fountain Square), there is a manhole cover on the ground. This is the entrance to the Royal Waterways.

  • Importance: This is arguably the most important use of a Simple Key for mid-game progression. The Royal Waterways lead to the Isma’s Grove (granting Isma’s Tear, which allows swimming in acid) and the Dung Defender boss fight. Without this key, you are forced to find much more obscure paths into the deeper sections of the kingdom.

3. The Pleasure House (City of Tears)

To the east of the City of Tears, near the elevator that leads up to the Resting Grounds, you will find a large building with a glowing sign. This is the Pleasure House.

  • The Content: Inside, you will find a Hot Spring (perfect for recovering Soul and Health), the ghost of Songstress Marissa, and the coward Poggy Thorax.
  • The Revenge: Most importantly, this is where Millibelle the Banker flees if she steals your Geo. If you deposited money with her and she vanished, you can find her here in the hot spring. Attacking her (she doesn't take damage, just bounces around) will cause her to drop all your stolen Geo, plus interest.

4. The Junk Pit Cocoon (Royal Waterways)

Deep within the Royal Waterways, to the far left, lies the Junk Pit. This area is filled with literal trash, but amidst the debris is a large, chained golden cocoon.

  • The Ultimate Unlock: Using a Simple Key here releases the Godseeker. By using the Dream Nail on the Godseeker’s fallen body, you gain access to Godhome.
  • Godhome: This is the game's ultimate challenge, featuring boss rushes (Pantheons), the Hall of Gods, and the true final endings of the game. You should generally save this for last, as it is pure endgame content.

Strategic Recommendation: Which Door First?

If you are a first-time player, the order in which you use your keys can affect your stress levels. Here is the recommended priority:

  1. The Royal Waterways: Open this as soon as you reach the City of Tears. It opens up the most content and leads to essential abilities like acid swimming.
  2. Confessor Jiji: If you find yourself losing your Shade frequently or are carrying a lot of Geo, this should be your second priority. It acts as a safety net.
  3. The Pleasure House: Use this when you need a break from the gloom. The hot spring is a great checkpoint, and getting your Geo back from Millibelle is a rite of passage.
  4. The Junk Pit: Save this for the very end. You won't be ready for the challenges of Godhome until your nail is fully upgraded and your charm collection is complete.

Troubleshooting: Why Can't I Find the Key?

A common issue reported by players, particularly in the City of Tears, is the "missing key" bug. However, in 99% of cases, it is not a bug but a misunderstanding of the room's layout.

  • Verticality: Many players check the floor of the City of Tears room and assume the key isn't there. You must look up. The alcove is tucked away behind wooden supports that blend into the background.
  • The Pale Lurker: If you can't find the fourth key, ensure you are actually in the hidden area behind the Colosseum. You have to walk through a wall that looks solid to find the path leading to the cliffs.
  • Sly’s Inventory: If Sly isn't selling the key, check if you’ve rescued him. If he’s in Dirtmouth but the key isn't there, you may have already bought it and forgotten you have it in your inventory.

Conclusion

The 4 Simple Keys of Hollow Knight are more than just collectibles; they are the threads that sew the disparate parts of Hallownest together. From the practical soul-retrieval of Jiji to the grueling boss gauntlets of Godhome, these keys represent the player's growing curiosity and their willingness to "poke around in places they don't belong," as Sly so aptly puts it.

Whether you are saving up Geo in Dirtmouth or chasing a crazed warrior through the ash of Kingdom’s Edge, each key you find is a step toward uncovering the full history of the Fallen Kingdom.

FAQ

Can I get more than 4 Simple Keys?

No. There are exactly four keys and four locks in the game. Once all are used, you cannot obtain more, nor are there any more doors to open.

What happens if I lose a key?

It is impossible to "lose" a key in the game files. It will remain in your inventory under the "Items" tab until it is used on one of the four specific locks.

Does the Shopkeeper's Key count as a Simple Key?

No. The Shopkeeper's Key is a separate quest item found in Crystal Peak. Giving it to Sly unlocks more items in his shop (like Mask Shards and Ores), but it cannot be used to open Simple Locks.

Is there a Simple Key in the Silksong demo?

The upcoming sequel, Hollow Knight: Silksong, features its own set of keys (often called Rusted Keys or Simple Keys in the files), but they are entirely separate from the items found in the original game.

Which key is the hardest to get?

The Pale Lurker’s key is generally considered the hardest because it requires navigating Kingdom's Edge and winning a chase-style boss fight, whereas the others are found through exploration or purchase.