Unknown

Unknown is an extremely dangerous planet (2-5 environmental hazards, some can be mildly annoying, some are deadly/irresistable). It is composed of randomly chosen biomes (both on the surface and underground), and can have almost any biome in the game (except Aether World biomes, etc.). It is more diverse than other randomized planets (Shadow and Super Dense), and can be of tier 5-10.
 * Outputs of Atmospheric Condenser on this planet are the same as on normal planets (Garden, Eden, etc.), regardless of the primary biome.

Environmental hazards
All Unknown planets have different hazards. For each planet that you visit, its hazards are revealed when you land on it for the first time.
 * The number of hazards is chosen randomly (2-5). The higher is the planet tier, the greater is the chance of getting more hazards.
 * Severity of hazards (e.g. Mild Cold vs. Extreme Cold) doesn't depend on tier.
 * Only 1 hazard can be chosen from each category (for example, Mild Cold and Extreme Cold are in "cold" category, so a planet can't have both of them at the same time).
 * Some hazards are irresistable. For example,  ("Overwhelmingly Maddening Atmosphere") is not blocked by any sources of Insanity immunity (Darklight Flower, etc.).

Temporal Instability
"Temporal Instability" hazard is unique to Unknown planets. It causes your health/energy/hunger/location to sometimes return to where these values were N seconds ago.

List of all possible hazards
These are internal IDs of hazards (e.g.  is Mild Cold and   is Extreme Cold).