Terran (Arid)

A rocky planet that kept its atmosphere but lost its surface water, or never had enough of it to keep. The interior is sand and stone at temperatures that kill in the open, and the population lives on the poles, in the highlands and over aquifers. Istryx is the class's own example: dune seas from horizon to horizon, a Khazrath tunnel network beneath them, and eleven million people living off water they do not talk about in front of strangers.

Planetary environment

Crossing it

Navigate: DC 15
Forage: DC 20
Notice: DC 10

Dunes shift, so charts go out of date. Water sets the schedule, and crossings are planned in nights.

Exposure

Extreme Heat

Temperatures above about 100 degrees Fahrenheit in shade, or anywhere near a working vent.

CON save, DC 10, rising by 1 for each hour after the first. End of each hour. One level of exhaustion.
- Sealed and armored
  
  A creature in medium or heavy armor, or in a sealed suit without active cooling, has disadvantage on the save.
- Water
  
  A creature with its full water ration has advantage on the save. One without any fails automatically.
- Cooled
  
  Active cooling, a Rift effect naming heat, or Resistance to fire damage removes the save.

In play

Water

Rations of water are tracked by the day instead of the week. A day in the open without shelter costs a level of exhaustion that only water and shade remove.
Moving dunes

The interior has no fixed landmarks. Navigation from a chart more than a season old has disadvantage, and a dune sea crossing is made at night or not at all.
Vibration hunters

Every creature here large enough to be worth hunting hunts by vibration. Moving at more than half speed across open sand gives every burrowing creature within a mile the party's position.

Regions on it

Desert Dry ground that loses more water than it receives, mostly rock and scrub with some open dune.
Highland Mountain country below the snow line: long sightlines, slow going and fast-changing weather.
Lower Atmosphere The layer of a world's atmosphere where weather occurs: breathable, turbulent and home to flying creatures and vessels.
Near Space The last of the atmosphere, thin enough to count as vacuum for every purpose except drag.
River Moving fresh water, and the fastest route across most terrain that has one.
Settlement Built ground, lived in or abandoned: close quarters, hard cover, and a jurisdiction attached to every encounter.
Storm Front Organized violent weather on the move, with high wind, whiteout and a visible advancing wall.
Subterranean Everything under the surface, with no light, no weather, and a route set by what the rock allows.
Upper Atmosphere The stratosphere and mesosphere, above the weather and below space, with no breathable air and little lift.

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