Armor (medium or heavy), uncommon
Years of use has worn away the stiffness and discomfort of this armor, allowing you to wear it without fatigue. You have advantage on Constitution saving throws made to endure a forced march. In addition, wearing this armor while resting doesn't impose any adverse effects, and if your rest is interrupted and you are forced to roll initiative, you gain a +10 bonus to the roll.
”That's the difference between me and you Private, you ain't got no endurance”