Cryotube

A cryotube is a rare structure that can occur randomly underground. Cryotubes are glass tubes that contain some sort of creature, which will be cryogenically frozen inside. Guaranteed cryotubes can be found in the cryobarrios of.

Generation
Cryotubes cannot appear in zones on the surface, but can occur in nearly any underground zone, with every zone having a small chance to contain one tube. This chance is equal to the following:

"Depth" as used here is how many strata levels below the surface the zone is. For example, the chance of a cryotube occurring in a zone 1 stratum below the surface is 0.3%. Cryotubes become guaranteed to generate in a zone (a chance of 100%) at 998 strata deep.

Structure
Cryotubes are small, sealed 5x5 structures, composed of and. They are filled with, and in their center will be a creature chosen randomly from a predetermined table, who will be frozen by the mist and will be unable to act.

Cryotubes have a chance to be "destroyed"; in this case, the glass walls of the tube will be found randomly scattered around where the tube generated, and will be. This will allow the cryogenic mist inside to disperse and eventually dissipate. No creature will be found inside the tube. There is a 5% chance for a puddle of to be amongst the wreckage.

Occasionally, otherwise intact cryotubes will lack sections of their walls, which will allow the mist inside to disperse and, eventually, will allow the creature inside to thaw.

Contents
Intact cryotubes will always contain a single creature, randomly chosen from a table, which will be frozen inside the tube and will be unable to act. While frozen, the creature will be completely immune to damage. To thaw the creature out, its temperature must be raised, or the cryogenic mist inside the tube must be allowed to disperse, which can be accomplished by removing a section of the tube's wall.

One of the following creatures will be randomly chosen to be placed inside a cryotube when it generates. Note that if "destroyed" is chosen, the cryotube will not contain a creature and will be destroyed as described above.