Core Theory

Core theory is a sub-theory that is reliant on the existence of the Tulpa effect. Essentially, you can have the Tulpa effect without Core theory but you cannot have Core theory without the Tulpa effect. This sub-theory was created by Robert of the blog White Elephants, and essentially states that, given Slender Man's status as a thoughtform, he can be defeated or possibly even killed by shifting the way the characters think of him, which Robert states is best done by framing it as a story with various heroes filling different roles.

Roles
The roles that Robert proposed for the Core Theory are as follows:

Sage: ''”There's a dark jungle next to the village. People who go into it never return. The villagers fear the jungle. Then one day a man with a torch goes in, the villagers scream at him to not, but he does anyway. He returns the next night, crawling back, bleeding to death, claw marks on his back. With his last breath he says 'Within the Jungle lives a Tiger, who is twelve feet long, obsidian claws, and has fire in its eyes...but it is just a Tiger and it bleeds.' After that he dies. The villagers no longer fear the jungle after that day. Oh, it's still scary and they take precautions from the huge Tiger...but it's just a Tiger. No longer is it Unknown or Shadows, perhaps one day someone will go and kill the Tiger...but there is no need for pointless fear.''”

Mystic: ”The Mystic can equal to -Veteran.- Mystic has fought, stores the knowledge of the past, and continues to give support when possible.”

Hermit: ”The Hermit lives by himself, has developed methods to survive, and is willing to pass on instructions, but has his own priorities, and odds are will not fight as opposed to run.”

Warrior: ''”Brave, Bold, Stupid in that headstrong way, Fights for the sake of the fight, Fights without fear, Only fights on This Side, Can push /Construct/ back to Other Side for a while, cannot beat it. A stop gap, and if they become an /Agent/ then there's going to be a lot of trouble.”''

Guardian: ”Calm, controlled with knowledge, FIghts for others BUT will have nothing left on This Side, FIghts on Other Side, Stays on Other Side and keep Him there for a much longer time, will return when the Vigil is over, or if a Hero emerges.”

Hero: ”Afraid but pushes on, Foolish but gains wisdom from Sages and Mystics, Fights for those who are important to him, Fights on both This Side and Other Side Only a Hero can kill a monster...but the Hero always dies at the end of the story.”

Bluelight (of Speaking of the Truth) later has begun adding new titles to Core theory:

Savant: ”A person of great and varied learning.”