The Chaser

"He's here."

- Kate's only quote upon encountering the Slender Man for a second time

Kate (last name unknown, assumed to be Hayes or Milens) is the main protagonist of the original Slender game and the secondary antagonist of its official sequel, Slender: The Arrival, acting as a brainwashed proxy who relentlessly chases the player.

Slender
Kate is the characterless protagonist of the first game, acting as the player controlled female who is tasked by herself to find eight mysterious notes spread throughout a forest. When seeking for these notes, Kate is hunted by the enigmatic Slender Man, who stalks and chases her. The player is caught by the mysterious kidnapper either way, setting up the events of the second game.

Slender: The Arrival
When Kate is reported missing, her friend, Lauren, arrives on the sight, looking for her former confidant. Lauren is hunted by the Slender Man as well before stumbling upon an abandoned mine shaft. It is in the shaft where Lauren discovers that Kate has been brainwashed to become the Slender Man's proxy. As such, the mindless villainesses hunts the player sided with her slender master. Lauren eventually escapes into a burning forest and is knocked unconscious by another proxy, Charlie. When she wakes up, she sees a normal Kate weeping in the corner. When Lauren approaches, Kate jumps out of her fetal position and brutally murders her before dragging her bloody corpse away.