Extremophile

You are resilient even in the most extreme conditions of heat, cold, high altitude, starvation, and dehydration, gaining the following benefits:

• Increase your Constitution score by 1, to a maximum of 20.
• You are automatically acclimated to breathing at all altitudes below 30,000 feet.
• You have advantage on Constitution saving throws against gaining exhaustion from extreme cold, extreme heat, frigid water, or not consuming food or water.
• You can move across and climb icy surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice or snow doesn't cost you extra movement.
• You need only one half gallon of water per day, even if the weather is hot. If you drink less than that much water, you must succeed on a DC 10 Constitution saving throw or suffer one level of exhaustion at the end of the day.
• You can go without food for a number of days equal to 5 + your proficiency bonus + your Constitution modifier (minimum 1). At the end of each day beyond that limit, you automatically suffer one level of exhaustion. A normal day of eating resets the count of days without food to zero.