High Altitude
Above 10,000 ft: CON save each 6 hours or gain exhaustion. 30 days to acclimate. Above 20,000 ft: must hold breath or suffocate.
Traveling at high altitude (above 10,000 feet / 3,000 meters) puts stress on the body due to thin air.
Breathing: Each hour spent at high altitude counts as 2 hours for the purpose of determining how long a creature can hold its breath and for exhaustion checks.
Acclimation: A creature can spend 30 days at high altitude to become acclimated. Acclimated creatures do not suffer the effects. Creatures native to high altitudes are naturally acclimated.
Effects: For each 6 hours of travel at high altitude, a non-acclimated creature must make a DC 10 Constitution saving throw or gain one level of exhaustion.
Extreme altitude (above 20,000 feet / 6,000 meters): The air is too thin for most creatures to breathe. A creature at extreme altitude without supplemental air or magic must begin holding its breath immediately.
Interaction with other hazards: High altitude often combines with extreme cold and difficult terrain (mountainous paths), creating compounding survival challenges.
Mitigation:
- Wind walk and flying bypass the need to climb
- Water breathing does not help (it's about air pressure, not water)
- Acclimation (30 days) eliminates the hazard
- Magic items that grant a breathable atmosphere