"As young soldier passes you on the road, he strips off his Leather armor and throws it at your feet. "I shall never fight again!" he declares."
The Leather is an artifact from Heroes of Might and Magic IV, giving heroes +5 Melee and Ranged defense.
The Leather the most rudimentary armor in the game, but also the cheapest. The good part about it is that, being so light, it doesn't reduce the mobility of the wearer (unlike other armors).
For its price, the Leather is an excellent method to increase your hero's survivability - until better armors are found.