The Boy

Phantom embodiment of all boys who died regardless of whether or not they died in the mines. Appears to seek vengeance on the living who were responsible for the death of boys. The Boy appears as a boy of varying ages, carrying a lantern and speaking with a man's voice. While supernatural, The Boy is neither of The Green nor of The Inner Dark; he is the first Independant who appears in the show.

The Boy's actions are detailed in Episode 5: The Boy, and he briefly appears in An Interlude: The Scenic Route.

The exact nature of who he targets is up for debate. All his victims to date have been adults, and he predominantly targets those who were responsible for boys dying in the mines, but Myrtle Hooper is an outlier in this regard.

While Myrtle Hooper killing her little brother doesn't involve mines--as a child, she hit him with a rock and he fell into the river, and it's not clear if he died from the blow to the head or from drowning--it does involve stones, and is the source of the minor theory that he targets adults who were responsible for boys dying because of stone or earth. The Boy also didn't appear to Myrtle until she was about to get married; this might be an argument for The Boy only targeting adults, or might be an argument for him acting to prevent Myrtle ever becoming a mother and having sons which she would fail to take care of.