Asaro, Indonesia and Papua New Guinea
Also called the Asaro Mudmen, the legend goes that they were defeated by an enemy tribe and forced to leg it into the Asaro River. They waited until the sun was on its way down before attempting escape. The enemy clocked them rising from the muddy banks covered in mud and assumed they were spirits. Most tribes in Papua New Guinea are proper terrified of spirits, so the enemy fled screaming, and the Asaro escaped.
The mud was thought to be poisonous so instead of covering their faces they made awesome masks.
☛ Now: Tribes #3: It Sucks To Be A Pygmy