Worn by members of the Sorrows tribe, the yao guai gauntlet is the right forearm of a yao guai worn like a glove rather than strapped to the arm of the user, as opposed to the deathclaw gauntlet.
Although a mid-tier Unarmed weapon, the yao gaui gauntlet lacks the damage of other weapons in its class, like the power fist or spiked knuckles. Its selling points however, are that it ignore damage resistance and threshold and it has a bonus critical multiplier and critical damage. Both of these make it a far more effective weapon.
It is the primary weapon of the Sorrows tribe, as each of the members completes a rite of passage to kill a yao guai and obtain a gauntlet for themselves. As such, it can most likely be looted off of the corpses of the Sorrows after their deaths.
It can also be bought from the Gun Runners after completion of the add-on.
↑The Courier: "Nice guns." Joshua Graham: "In the Great Basin and Colorado Plateau, all tribes are known for a specific weapon. White Legs are known for their big submachine guns, "storm drums." They broke into an armory near Spanish Fork and have been using them for years. Of course, the Dead Horses have their wooden war clubs and even the Sorrows have their Yao Guai gauntlets. This type of .45 Automatic pistol was designed by one of my tribe almost four hundred years ago. Learning its use is a New Canaanite rite of passage." (Joshua Graham's dialogue)