Skull Cavern
The Skull Cavern is located in the northwest area of the Desert. It is initially locked and requires the Skull Key to gain access. After entering the Cavern for the first time, a letter is received on the following day, from Mr. Qi. The letter begins the quest Qi's Challenge, which is completed by reaching floor 25 in the Skull Cavern. Completing the quest awards 
10,000g (Delivered by mail the following day). If the player reaches level 25 of the Skull Cavern during the first visit, the quest will automatically be fulfilled the next day.
There is no limit to the number of floors, or levels, in the Skull Cavern (at least until the integer limit of 2147483647 is reached). Similar to the Mines, the player advances through floors in the Skull Cavern by finding a ladder on each floor, either by mining rocks or defeating enemies. The player can sometimes find a shaft, or hole, which makes it possible to skip 3-15 floors. Jumping down the shaft causes health damage equal to 3x the number of levels skipped (although jumping down a shaft will never reduce health to less than 1).
Unlike the Mines, there is no elevator to save progress, but on every floor there is a ladder at the starting point where you can leave the Skull Cavern. Each visit must start again from the first floor. If the player runs out of health or passes out while exploring Skull Cavern, they will wake up sometime later on the same day, in Harvey's Clinic. A fee of 1,000g will be deducted for emergency surgery. Some items may also be lost.
The chance to find Iridium Ore increases steadily as you descend into the Skull Cavern. The monsters in the Cavern also have a chance to drop ore and Iridium Bars. It can be a good idea to bring the Lava Katana or Galaxy Sword, as enemies are particularly strong. High Luck increases the frequency of ore veins and the appearance of ladders/holes. Rapid descent to floors with a higher chance of spawning Iridium Nodes is often more efficient for acquiring ore than thorough exploration. With a full inventory of stone, it's possible to craft staircases to descend to floor 300+.
The plaques that can be occasionally found on the walls contain enciphered messages.
Time
Time runs more slowly in Skull Cavern than elsewhere in the game: whereas one hour of game time normally lasts 42 seconds, in Skull Cavern one hour lasts 54 seconds. However, time reverts to normal 42-second hours in multiplayer games and on Prehistoric Floors.[1] This has two main implications:
- Players have more real-time available before the end of the day, and should be able to descend deeper than otherwise.
- The game-time duration of any buff is decreased.
This adjustment in timing has no effect, however, upon other aspects of the game, such as equipment processing times. For example, Honey placed in a Keg at noon is ready with Mead at 10 pm even if the player spends most of that time in Skull Cavern.
Preparation
Food
Shown below are foods with buffs that are useful when exploring the Skull Cavern. Note that eating a food with buffs will wipe out any active buffs and replace them with the buffs from the newly eaten food. If the newly eaten food has no buffs, the existing buffs will remain in effect. Coffee and Triple Shot Espresso are an exception to this rule; they will stack with other food buffs (but not each other).
Explosives
Bombs make quick work of densely-clustered stones and ore veins. They're also necessary for permanently defeating Mummies.
- Buy Cherry Bombs from the Dwarf for 300g or craft them with 4 Copper Ore and 1 Coal.
- Buy Bombs from the Dwarf for 600g or craft them with 4 Iron Ore and 1 Coal.
- Buy Mega Bombs from the Dwarf for 1,000g or craft them with 4 Gold Ore, 1 Solar Essence, and 1 Void Essence.
The Slingshot's Explosive Ammo is also effective in dealing with small groups of stones, Iridium Ore deposits, and incapacitated Mummies. Loading the Slingshot with Gold Ore deals substantial damage, making it potentially useful for dispatching tough targets. Explosive ammo can be crafted or bought at the Adventurer's Guild for 300g.
Staircase
- Staircases can be used for rapid descent or skipping troublesome floors.
Rings
Warp Totems
- A Warp Totem can be used to make a quick exit if supplies are running low or the day is almost over.
Monsters
| Image | Monster | HP | Damage | Notes |
|---|---|---|---|---|
 |
Armored Bug | 8 | Cannot be killed. | |
 |
Big Slime | 60 | 5 | Splits into smaller Slimes when killed. Big Slimes are usually purple in the Skull Cavern. |
 |
Purple Slime | 410 | 28 | Can drop Iridium Ore, Iridium Bar |
 |
Lava Bat | 80 | 15 | Appears rarely; flies. |
 |
Mummy | 260 | 30 | Needs to be finished with a bomb of any type after being knocked out with other weapons. If a bomb does enough damage to knock the Mummy out, it will also destroy it. |
 |
Serpent | 150 | 23 | Moves quickly; default flying enemy. |
 |
Iridium Bat | 300 | 30 | Appears at level 50+. Very high HP and Damage. |
 |
Iridium Crab | 240 | 15 | Appears at level 26+. |
 |
Carbon Ghost | 190 | 25 | May appear on Mummy levels. |
 |
Pepper Rex | 300 | 15 | Appears mainly on prehistoric floors; breathes fire. |
Prehistoric Floors
Prehistoric floors are a type of infested floor containing mainly Pepper Rex monsters. Mutant flies and Iridium Bats can also attack the player there. Dinosaur Eggs and Fiddlehead Ferns can be foraged on Prehistoric floors.
Treasure Rooms
Small rooms containing treasure chests, similar to those in The Mines, can randomly appear at level 10+. Daily luck and Luck Buffs affect the chance to find Treasure Rooms. Obtaining the Special Charm also increases the chance to find Treasure Rooms.
Below is a collapsable table of all possible treasures that can be randomly found inside Treasure Chests in the Skull Cavern.
Secret
After reading Secret Note #10, the player will find Mr. Qi at level 100 of the Skull Cavern. A cutscene ensues in which:
| Details |
|---|
| Mr. Qi will either congratulate the player for reaching level 100 while using 10 or less Staircases or say the player is "clever" but not "honorable" for using more than 10. In either case, he will award the player with Iridium Snake Milk, which permanently increases the player's Health by 25 points. |
History
- 1.3: Added Carbon Ghost, Iridium Bat, Iridium Crab, treasure rooms, and encounter with Mr. Qi. Removed exploit that allowed the player to avoid bomb damage by consuming food after placing a bomb.
- 1.4: Added Pepper Rex. Added White Turban to possible Treasure Room items. All players entering a chute in Multiplayer now descend to the same level. Qi's challenge can now be completed during the first visit to the Skull Cavern. Chutes will no longer drop the player past level 100 if the Secret Note cutscene has not occured.
References
| Locations | |
|---|---|
| Locations | Backwoods • Beach • Bus Stop • Calico Desert • Cindersap Forest • Farm • Farm Cave • Farm Pond • Graveyard • Ginger Island • Mastery Cave • Minecart • Mines • Mountain • Mutant Bug Lair • Pelican Town • Quarry • Quarry Mine • Railroad • Secret Woods • Sewers • Skull Cavern • Summit • Tunnel • Volcano Dungeon • Witch's Swamp |