This guide concerns sustainable life underground - in Caves and Ruins. Sustainable life means being able to survive for an indefinite period of time without needing to exit the current level. The guide contains instructions and opinions on the matter, and every player is free to find their own playstyle and methods for achieving the goal of sustainable underground life.
Basics of the underground environmentEdit
Caves and Ruins are free from all weather - it is permanently Summer, with a constant temperature and no Rain or Lightning. Occasionally, Earthquakes can happen on both levels, which drop Rocks, Flint, Nitre, Gold Nuggets, Red Gems, Blue Gems, or Marble, but the falling minerals will damage the player if they manage to directly hit them. It is permanently dark, and the player loses 5 Sanity per minute, regardless of the time of day. So better have a base up there too and make a lot of pumpkin cookies (see taffy recipe) or taffy.
Caves have a day and night cycle, as well as a Moon Cycle, although neither is clearly visible (there is no clock in the top right corner of the screen). The current state could be determined by listening to the music and by checking into a shaft of natural light. The shafts of natural light are patches of ground where light reaches from the surface. They could contain Evergreens, Grass Tufts, Saplings, or Berry Bushes, or they could be in an underground Marsh.
Ruins have no day and night cycle - it is permanent night for gameplay purposes. This means that surface animals that have been brought down - Pigs, Rabbits, Bees, Beefalo, or Flying Birds - are always asleep. Instead, there is a Nightmare Cycle, which alters the appearance of the place and causes Shadow Creatures to spawn from Nightmare Lights and Nightmare Fissures. There are no shafts of natural light and there is no way to tell what time it is. The Moon Cycle still affects the Ruins, albeit invisibly.
Before being able to live sustainably and indefinitely underground, one needs to gather all the non-renewable resources, required for sustainable life above ground. These include, but are not limited to: Grass Tufts, Saplings, Berry Bushes, Honeycombs, Bees, Pine Cones, Pigskin, Seeds, Fleshy Bulbs, and a living Flying Bird. These would enable resources, such as Grass, Twigs, Berries (with occasional Gobblers), Honey and Bees, Logs and Living Logs, and Pigskins to become renewable underground. The remaining resources, required for the construction of a camp underground, such as Gold and Rocks are already renewable and highly abundant there.
Location of the campEdit
In Caves, there are shafts of natural light containing Evergreens, Grass Tufts, Saplings, and Berry Bushes. Rarely, the Shaft could also contain a version of the Cave Camp Set Piece, which includes a Frog Pond. These shafts are a good place for the camp (except if the shaft contains a Pond, in which case Frogs will be a constant nuisance). Try to place your Tent inside such a shaft, so when you sleep and your fires are extinguished, you don`t wake up in total darkness.
In Ruins, there are no shafts of natural light, and there are Nightmare Lights and Nightmare Fissures, which will spawn Shadow Creatures during the Nightmare Phase. The camp should be placed as far away from any Nightmare Lights and Fissures as possible. A good camp location is on the edge of a Light Flower field. Walls (upgraded at least once) could be used to keep Shadow creatures from randomly wandering inside the camp. Try to place the Tent by a Light Flower, so when you sleep and all your fires are extinguished, you don`t wake up in total darkness.
Keeping the lights onEdit
Probably the highest priority in Caves and Ruins is to always have access to a source of light. Without a source of light, one is vulnerable to attacks from Charlie and cannot do almost anything.
For a mobile source of light, the best ones are the Miner Hat and the Lantern. Both are refuelable (with Slurtle Slime, Fireflies, or Light Bulbs) and both could be used in such a way that you could swing a weapon while still having light. The Miner Hat prevents you from wearing head armor, but it keeps your hands free. The Lantern allows you to wear head armor, but has to be placed on the ground before equipping a weapon, and at that point it becomes a static light source. It could also be stolen by Splumonkeys if put on the ground, which causes it to stop emitting light.
For fueling the Miner Hat and Lantern, one could use Fireflies, Light Bulbs and Slurtle Slime. Fireflies are not renewable, so it is not a good idea to use them, unless there is no alternative. Light Bulbs and Slurtle Slime are both renewable. A Slurtle Slime grants 45 seconds of light and can be stored without spoiling. The Light Bulb grants 90 seconds of light, but spoils in 6 days. If the Light Bulbs are kept in the inventory (and not in an Ice Box) and the Miner Hat or Lantern is lit for the entire time, one needs 32 Light Bulbs (at 0% spoilage) to have light for the full 6 days before they spoil. Any additional Light Bulbs picked are a waste of resources.
As for static light sources, a Firepit is the best one for Caves. If Beefalo have been brought from above, Beefalo Wool or Manure could be used as easy to obtain and renewable fuel sources. Otherwise, Logs could be burned as well. For the Ruins, due to the abundance of Nightmare Fuel, the Night Light is a very efficient static light source.
Keeping Sanity upEdit
Unless you`re playing as Maxwell, you will need to replenish your sanity in one way or another. Remember, you`re trying to be completely self-sufficient for an indefinite period of time inside the Caves or Ruins, so items like the Dapper Vest, the Tam o` Shanter, the Sewing Kit, and Mushrooms are not renewable ways to keep sane.
As with above ground, sleeping can provide an instant sanity boost, albeit at the cost of hunger. Before choosing this method for staying sane, one must ensure a steady food supply or at least a good stockpile of food. It is important to be noted that when sleeping, a Miner Hat or a Lantern will still lose fuel, and all fires (including Night Lights) will be immediately extinguished. If the Tent or Bed Roll is used while there is no natural light around, and the equipped light source does not have enough fuel to last until the next day, the player will wake up in total darkness, which could nullify any sanity gain and cause Charlie to attack, if a light source is not found quickly enough. In order to counter this, in Caves one could sleep in a shaft of light, or near a Light Flower or Mushtree. In Ruins, the available options are near Light Flowers, or near an Ancient Pseudoscience Station. Additionally, to avoid losing fuel for the mobile light sources, they could be unequipped.
It is worth noting that sleeping in the Ruins will advance time to the next stage of the Nightmare Cycle, but may prevent Shadow Creatures from dying if time is advanced from Nightmare to Calm. In this case, the creatures will die in the next cycle.
Most clothing items which restore sanity are non-renewable in Caves and Ruins, because in order to keep them repaired, one needs a Sewing Kit, which requires Hound`s Teeth - a nonrenewable resource underground. However, it is possible to recover Sanity through clothes alone while keeping them renewable (sort of). A Top Hat is a renewable item of clothing and restores 3.3 Sanity per minute. The Thulecite Suit, which can be crafted in the Ruins and brought to the Caves does not degrade (unless actively used as armor) and also restores 3.3 Sanity per minute. Together both items restore 6.6 Sanity per minute; more than the constant sanity drain inside Caves and Ruins.
Any of the Crock Pot Dishes will restore 5 sanity, but in order to efficiently keep sane, one can rely on the Pumpkin Cookie, Taffy, or Jerky / Small Jerky, which restore up to 15 Sanity each (Small Jerky restores 10).
Cut Grass and TwigsEdit
In Caves, Grass Tufts and Saplings could sometimes be found in shafts of light, making Cut Grass and Twigs renewable.
In Ruins, if Grass Tufts and Saplings are brought from above, Cut Grass and Twigs could be made renewable.
Logs and Living LogsEdit
In Ruins, if Pinecones have been brought from above, Logs could be made renewable. Cutting down Evergreens could spawn a Treeguard, so Living Logs could also be made renewable.
In Caves, sometimes there could be underground marshes, containing reeds.
In Ruins, there is no way to obtain Reeds, or to make them renewable.
Minerals and GemsEdit
In both Caves and Ruins, Rocks, Flint, Nitre, Gold, and Marble are renewable through Earthquakes. Rocks and Flint could also be obtained from Rock Lobsters. Of the Gems, only the Red Gem, Blue Gem and Purple Gem are renewable.
If Beefalo have been brought from above, they can be shaved at night or killed for Beefalo Wool. In Ruins, because the Beefalo are permanently asleep, they could be shaved at any time, as long as their wool has grown back.
Here will be listed some of the available renewable food sources in Caves and Ruins.
In Caves, Meat could be obtained from Bunnymen, Beefalo (if brought from above), Pigs (if brought from above or if Pig Houses are constructed), and Rock Lobsters, all of which are renewable. The only way to renewably obtain Morsels in Caves is to kill baby Beefalo that have been brought from above or rabbits that fall during earthquakes.
In Ruins, Meat could be obtained by Rock Lobsters (if brought from above), Beefalo (if brought from above) and Bunnymen. Pigs will not leave their houses in the Ruins, because it is considered permanent night. The Beefalo will be permanently asleep, but can still reproduce and be killed for Meat. Morsels can be renewably obtained from Splumonkeys.
Jerky / Small JerkyEdit
One could build Drying Racks underground to obtain Jerky and Small Jerky, which is a great way to stay well fed and sane at the same time.
Berries and GobblersEdit
Caves sometimes contain Berry Bushes, so a berry farm could be created there. Gobblers could spawn and eat the berries as in the world above. Walling off the farm would make it easier to kill any Gobblers that spawn. The only renewable ranged weapon underground is the Boomerang, so this could be used as well.
For Ruins, if Berry Bushes have been brought from above, a berry farm could be created there as well. Because it is permanent night, any spawning Gobblers will immediately return inside the bush that spawned them.
If Honeycombs and Bees have been brought from above, bee boxes could be constructed underground. However, both in Caves and Ruins, the Bees will never come out to gather from flowers. In Caves, the Bees could be forced out by harvesting their box and will remain out until Dusk, gathering from nearby flowers, if one has planted butterflies. In Ruins, the Bees could also be forced out by harvesting the box, but will immediately return inside once they disengage the player.
Instead, if the Bee Boxes are built far enough away from the camp, then the game will switch to a simplified model of honey production, producing one honey per day.
Fish, Frogs, and EelsEdit
In Ruins, there are always ponds, which could be fished for Eels.
Eggs and SeedsEdit
Vegetables and FruitsEdit
In Ruins, crops will not grow on their own and require fertilization. Manure, Rot and Rotten Eggs are renewable fertilizers in Ruins (Manure is dropped by Splumonkeys as a form of ranged attack).
In both Caves and Ruins, Seeds have to be brought from above and renewed through feeding some of the crops to a caged bird.
Bananas and LichenEdit
Ruins have two unique renewable food sources - the Cave Banana and the Lichen. The Bananas grow on Cave Banana Trees and are dropped by Splumonkeys. The Lichen grows randomly in certain areas of the Ruins. Both of these food sources are impossible to relocate and therefore are only found in the ruins.
A crock pot could be constructed underground, both in Caves and Ruins, and give access to all crock pot recipes that could be made with the available ingredients. Notable useful dishes are Taffy and Pumpkin Cookie - for sanity restoration; Meatballs, Honey Ham, and Dragonpie - for efficient nutrition; Fishsticks (always available in Ruins and sometimes available in Caves) - for healing.
While not a good food item on its own, Monster Meat could be used as an ingredient in many Crock Pot Recipes, as well as fed to a caged bird for eggs. It is made renewable through the attacks of Depths Worms and through killing Spiders, all of which are abundant in both Caves and Ruins.
If Fleshy Bulbs have been brought from above, a Lureplant could be planted underground, enabling the renewability of Leafy Meat. A good location for a Leafy Meat Farm is on Cave Rock Turf or Rocky Turf, in order to make it easier to collect the Leafy Meat.
Tools, weapons and armorEdit
Because Gold, Flint, Twigs, Cut Grass and Rocks are all renewable in Caves, all tools are renewable there. As for Ruins, one needs to bring only Grass Tufts and Saplings in order to make all tools renewable. It should be noted that Gold tools are a more efficient use of Twigs, therefore they are preferred over the Flint ones.
Of the armor, all except the Thulecite Suit and Thulecite Crown are renewable in Caves. In Ruins, no armor is renewable, unless Grass Tufts and Pine Cones have been brought from above, in which case the Grass Suit, Log Suit, Marble Suit, and Beekeeper Hat could be made renewable.
With the right preparation, it is possible to survive indefinitely underground. Of course, non-renewable items could also be brought to make the experience far easier - for example a Tam and a stack of Hound`s Teeth, which will last for a very long time (although not indefinitely). Although there is no real point in prolonged life underground, it can be a good challenge and could diversify your Don`t Starve experience.