Chaser

The Chaser is the proxified version of Kate. It serves as the secondary antagonist of Slender: The Arrival and the primary antagonist of The Chaser (hence the game's title).

Slender: The Arrival
The Chaser makes its first appearance in Chapter 3 of Slender: The Arrival, "Into The Abyss". It is unknown what happened to Kate, but she now seems feral and wears a mask and has a black substance around her eyes and mouth with very pale skin, possibly due to residing in the mines. Her hoodie and hands are also heavily stained with blood; it is unknown whose blood it is. It appears that her eyes are very sensitive to light, as she gets dazed when Lauren concentrates her flashlight's beam towards her face. She also appears to snarl and growl. She aggressively chases Lauren as she activates the six generators until Lauren finally activates them all and gets on the elevator to escape.

In Chapter 5: "The Arrival", after Lauren gets knocked out by a proxified Charlie, Lauren wakes up in a room with him. After collecting a book, Charlie disappears, and the crying of Kate is heard. Lauren finds a normal Kate (unmasked and unhooded as well as looking badly burned) crying in a corner. Lauren approaches Kate, only for her to turn back into the Chaser and kill Lauren .The last shot of the game shows Lauren's limp body being dragged away by either Charlie, Slender Man, or the Chaser.

The Chaser
Hence the game's title, the Chaser will return as the main antagonist of the upcoming indie survival horror game, The Chaser. Similar to in The Arrival, she will keep chasing the player until they've collected all six gas canisters and have activated all of their corresponding generators.