I teased a bit of EJ's lore in my Part One of Creepypasta theme songs, so here's the lore!

He retains his original backstory, just with it tweaked so that the group is made up of people that offered Jack a place in their friendgroup.

He went out to meet them, then got knocked out, finding himself in a cult situation, gets himself sacrificed, loses his eyes as an offering to the demon since Jack insulted it, rather than as an actual step. 

After that, it pretty much veers off into my own interpretation of his lore. He still takes kidneys, but takes other organs that won't kill whoever he takes from, since he detests hurting others, and is very fond of children, originally wanting to go into being a child surgeon to help kids in need. 

But, after becoming possessed by the demon; Chernobog, he no longer could show his face in a normal setting ever again.

Slender brought Jack to his side at first, promising him an end to his insatiable hunger, but very soon, Jack realizes that Slender is a soul devouring monster who feels no remorse, killing children and not caring after luring them to their deaths. 

Jack rebels in his own way, children's souls who have died alone in the woods shall be guided to the afterlife, the ether if you will.

Donning his black hoodie, blue mask, and a ghostly lantern, he takes the souls to a cave deep in the woods, inside of the cave, the souls are guided into a void that leads into eternal rest, created by Jack through a magic spell (Yes this universe has magic)

Jack tried to convince Toby that Slender was a terrible creature, but Toby was too far engrained into Slender's control to listen, and Jack was the only one who KNEW Slender kept killing Toby because he wouldn't stop regaining his memories, even though Slender's erased them many times.

Both Toby and Jack have the Proxy Intitative symbol branded onto their hands, meaning they belong to The Slenderman for the rest of their lives, and for Jack, that would be a long time...Because he will be possessed for all eternity. 

For Jack, the branding was painful and unwanted, but for Toby, he was eager to do it, and since Toby can not feel pain, it wasn't bad at all. 

And since Toby and Jack are on opposing sides, it makes everything complicated, even though Jack cares for Toby very much, seeing him as family. 

So basically, EJ is a big hearted, demon possessed, soul guiding savior. 

Hope y'all like his rewritten lore.