**Conditions.** Traveling at altitudes of 10,000 feet or higher above sea level is taxing for most creatures because of the reduced amount of oxygen in the air. **CON Saving Throws.** Creatures not acclimated to [[High Altitude]] have [[Disadvantage]] on CON Saving Throws. **Shorter Travel Time.** Each hour such a creature spends traveling at high altitude counts as 2 hours for the purpose of determining how long that creature can travel (see "[[Travel Pace]]"). **Acclimation.** Creatures can become acclimated to a high altitude by spending 30 days or more at this elevation. Creatures can't become acclimated to elevations above 20,000 feet unless they are native to such environments.