Caves

Caves are an unimplimented/speculated area being added on the May 21st update. They will be worked on for another three updates until around July.

History
The video of the End of the Beginning update contained a unusual sound at the ending, which caves and underworld regions were hinted at. After processing the sound, the link derived was:-  [] ...

They were shown on May 10th at 10:00am PST during a twitch.tv live stream. Caves will be released to testers within on Monday the 13th of May or Tuesday the 14th of May

Features
The following features are confirmed for the pre-alpha caves only and may or may not be implemented in the final versions.

Cave Exclusive Features
Features that are shown in pre-alpha footage.
 * Caves will be entered via Plugged Sink Hole.
 * Caves contain limited natural light.
 * Earthquakes
 * No Day-Night Cycle. The Cave will be constantly 'night'.
 * New Mobs including:
 * Batilisks
 * Slurtle
 * Snurtle
 * Bunnymen (Underground equivalent of Pig Men.)
 * Cave Spiders
 * Spitters (a type of cave spider)
 * New clothes including Slurtle Shells.
 * Dying in the cave respawns the player outside, similar to Adventure Mode.
 * New explosive (uses slurtle slime)
 * New light sources including:
 * Sun rays from the surface
 * Mushtrees
 * Light Flowers
 * Lanterns
 * Guano, Underground equivalent of Manure.
 * Caves contain Berry Bushes, Saplings, and Grass just like on the surface. (only in sinkhole areas)

Unconfirmed Features
These features were hinted at or suggested but not confirmed. This is a temporary place for these features only put for informational purposes and are likely to be moved or removed.
 * Concept for monsters that attack hunger/add status effects.
 * Nightmare worlds from low Sanity.
 * Possible extra uses for Gunpowder including bombs and guns
 * Branching Science tree including additional Science Machines.
 * Different layers of caves.
 * Bunny King
 * Lava
 * Vampire sword
 * The Tentacle's body.