Natural Athlete:
You have proficiency in the Athletics skill.
Stone's Endurance:
You can focus yourself to occasionally shrug off injury. When you take damage, you can use your reaction to roll a d12. Add your Constitution modifier to the number rolled, and reduce the damage by that total. After you use this trait, you can't use it again until you finish a short or long rest.
Powerful Build:
You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift.
Mountain Born:
You're acclimated to high altitude, including elevations above 20,000 feet. You're also naturally adapted to cold climates, as described in chapter 5 of the Dungeon Master's Guide.
Languages:
You can speak, read, and write Common and Giant.