Duergar's iron fist

While wearing this gauntlet, your unarmed melee attacks with this hand deal 1d8 bludgeoning
damage instead of just your strength modifier. In addition, if the creature you hit is Large or
smaller, you can use your bonus action to force it
to make a successful Strength saving throw (DC
equals 8+prof.+STR mod) or be pushed up to 30
feet in a straight line, take 3d6 bludgeoning and
fall prone. Each time this ability is used, there is a
10 percent chance the gauntlet loses this ability permanent