Undercave

The undercave is a sprawling cave network located underneath a colony, accessed by entering a pit gate, which is filled with fleshbeast entities.
== Summary == 
In order to enter the undercave, the colony must have a pit gate open in a prior event. The undercave is not a conventional quest site and does not appear on the world map, meaning you cannot caravan inside normally. Furthermore, pawns within the undercave cannot be added to newly formed caravans. However, an option to form a specialized caravan into the undercave can be accomplished by selecting "Enter pit gate" while inspecting the pit gate structure on the home tile.
A map will be created once the first colonist is sent inside to explore. Exploration begins at a random point in the tile, where a pit gate exit is spawned. On the same tile, a section of unrevealed cave will house a dreadmeld which must be defeated to close the pit gate. To progress farther within the caves, fleshmass must be damaged to create passageway or the rock walls must be mined out to make tunnels through the ground. A warning letter will alert the player when a colonist is close to the dreadmeld's position. Prior to defeating the dreadmeld, the cavern will be able to be explored at will, at the cost of potential fleshbeast raids.
Once the dreadmeld is defeated, the undercave will become unstable, giving any pawns 10 hours to evacuate the tunnels. As this timer approaches zero, rock falls consisting of collapsed rocks will become more and more common. These may potentially damage pawns or items, or block routes back towards the exit. Anything remaining within the caves after this timer expires will be lost forever, including colonists. Once the undercave collapses, the pit gate will disappear which prevents reentry.
== Design ==
The undercave is a 100x100 map tile consisting of winding caves filled with fleshmass and fleshbeasts. The entire area is classified as being underneath overhead mountain and sits at a constant 15°C (59°F). Insects and Hives can be found within the cave system, albeit rarely.
The pit gate exit is a 3x3 structure consisting of a rope line back to the surface, and is generated when the first colonist enters the area. It is the only method of returning colonists safely to the surface. A clear area with a radius of 5 tiles will be generated around the created exit. Colonists may return here to the rope and interact with it to return to the surface.
The cave network is generated similarly to how caves spawn within mountainous regions. Stone found within these caves may be different compared to the stones native to the tile where the pit gate originates. Ore veins will appear underground and can serve as an alternative to a long-range mineral scanner or ground-penetrating scanner. Underground plant life may also be encountered, all of which are listed below.
Most of the cave system is choked by large amounts of fleshmass which must be burned or attacked to advance. Within these walls, flesh bulbs can be found that light the immediate area, and flesh sacks which may contain a varied assortment of loot. Once the caves become unstable, most of the fleshmass will gradually dissolve which may reveal new areas not explored previously. These areas may or may not contain more enemies which can overwhelm groups if released in quick succession.
Much of the cave floor is made up of various stone types, or a flesh flooring wherever fleshmass was previously cleared from. Occasionally, patches of shallow water may be found that can impede movement. Rarely, one might find patches of rich soil with wild healroot growing from it. This may be harvested if the plants are mature enough, but will not grow further due to the lack of adequate sunlight.
The entire border of the map will not contain fleshmass and will always be surrounded in a type of stone wall. This wall may still be mined past like any other to reach the map edge. Strangely, the green border used to escape a tile found while attacking faction settlements will appear if any bordering rock wall is destroyed. However, this cannot be utilized as an escape method from the caves. It is unknown whether this is intentional or not.
=== Structures ===
 
All of the following structures may be found within the undercave:
* Fleshmass - A fleshy barrier which must be destroyed to grant passageway.
* Plants - Several forms of plant life can be found within the undercave:
** Agarilux
** Wild healroot - Found rarely within patches of rich soil underground, will not grow due to lack of sunlight.
** Timbershroom 
* Ruins - Similar to the structures found above ground, multiple man-made buildings can be encountered within the caves. Examples:
** Ancient generator 
* Flesh sack - Containers made from the same flesh as the surrounding growths they are typically encased in. A pawn may attack the pod which will then drop its contents on the floor nearby. For a list of potential contents, see here.
=== Dangers ===
Some sections of the caves might contain enemies. These foes may be asleep upon discovery and might wake up if the area is entered or a disturbance is caused.
Enemies that can possibly spawn within the caves:
* Fingerspike
* Trispike
* Toughspike
* Bulbfreak
* Dreadmeld
The similarly themed fleshmass heart will not be encountered within the undercave.
== Analysis ==
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