The maze hidden beneath Sell Lemons contains two of the most valuable permanent upgrades currently available. By completing a series of lever puzzles, players can unlock the Sewer Key for the Cosmic Vine and the UFO Key for improved investor rewards.
Both keys are found inside the same maze system, but each requires a different lever sequence and reward path. Here’s a complete walkthrough.
Sewer Key Overview
The Sewer Key is used to unlock the Cosmic Vine.
Once activated, the Cosmic Vine provides an additional source of money that can be collected periodically, making it a valuable upgrade for long-term progression.
Completing this puzzle also rewards the Cosmic Farmer badge.
Sewer Key Lever Order
Inside the sewer maze, you’ll encounter four colored levers:
- Blue
- Red
- Green
- Purple
To unlock the Sewer Key, activate them in the following sequence:
- Pull Blue
- Pull Red
- Pull Green
- Unpull Red
- Unpull Blue
- Pull Purple
- Pull Red
After completing the sequence correctly, the Sewer Key will spawn within the maze.
Where to Find the Sewer Key
Once the final Red lever has been activated, a previously inaccessible section of the maze becomes available.
Follow the newly opened route until you reach the key’s location. Pick it up to receive the Sewer Key.
After obtaining it, return to the Cosmic Vine area and use the key to unlock the feature permanently.
UFO Key Requirements
Before attempting the UFO Key puzzle, you must first obtain the Alien Investor.
This requirement is extremely important because the UFO Key will not appear unless the Alien Investor has already been unlocked.
If you complete the puzzle and cannot find the key, this is usually the reason.
UFO Key Benefits
The UFO Key upgrades investor rewards.
According to the update, investor rewards increase from 1% cash to 2% cash after completing the UFO Key questline.
This effectively doubles the bonus provided by investors.
UFO Key Lever Order
To make the UFO Key appear, complete the following lever sequence:
- Pull Blue
- Pull Red
- Pull Green
- Unpull Red
- Pull Purple
- Pull Red
- Unpull Green
- Pull Red
Once the final step is completed, the UFO Key can be found deeper within the maze.
UFO Key Location
After finishing the lever sequence, travel to the UFO Key spawn area.
Remember:
- The key only appears if you own the Alien Investor.
- Players without the Alien Investor will see nothing at the location.
Collect the UFO Key when it appears.
Giving the UFO Key to the Alien
After obtaining the key, you’ll need to complete one final puzzle sequence.
Activate:
- Pull Red
- Pull Green
With those levers set correctly, travel to the Alien NPC and interact with it while carrying the UFO Key.
Handing over the key completes the quest.
Rewards
Sewer Key Rewards
- Unlocks the Cosmic Vine
- Additional passive income source
- Cosmic Farmer badge
UFO Key Rewards
- Unlocks the Good Samaritan badge
- Increases investor reward bonus
- Upgrades investor cash bonus from 1% to 2%
The maze is one of the more complicated puzzles in Sell Lemons because it requires both pulling and unpulling levers in specific orders. If a key doesn’t appear, double-check your lever sequence and make sure all requirements have been met.
For most players, the Sewer Key should be the first priority since it unlocks the Cosmic Vine. Once you have the Alien Investor, you can return for the UFO Key and secure the permanent investor reward boost.