Slender: The Arrival features a hidden level which can be reached from the prologue, as long as you have an updates version of the game (at least 1.2). Approach the swings on the playground by the house so that Lauren remembers how she used to play there with Kate when they were both young. Afterwards enter the building and keep playing the piano until the woman state that the melody brings back memories. Take the flashlight and turn on the radio.
Head outside and head to the tree with the poster regarding Charlie. The game will return to the main menu. Choose the "start game" option, but don't choose a scene. You will a message saying "I'm lost. Can you find me?". You will play hide and seek with Slender Man, running around the house. The game will once again return to the main menu, choose "start game" again. The hide and seek continues. This time Slender Man is looking for you. Wander around the house and when the monster reaches you, the scenery will change. You will see the last moments of one of the heroes. After the "You are dead" sign appears once again, choose "start game" and watch the final scene.
Additionally version 1.3 includes an additional chapter called "Genesis" in which you control Kate in a forest. It's a remake of the free version of Slender: The Eight Pages which required you to collect the title 8 pages.
There are 10 locations where you can find them:
- The silos
- The rocks
- The cross-shaped walls
- The stone pillars
- The tunnel
- The ruined lavatories
- The tanks
- The cistern
- The barrack with a car beside (on the wall of the barrack)
- The tree trunk (the tree can be distinguished from the others, it has a much thicker trunk)
All of you who have played Slender: The Eight Pages will clearly see that it's the same map, just with nicer graphics. The locations stay the same: the latrines are in the middle of the map, to the right of them there are the tanks. To the left of the starting point there's a tree and to the right a silos.
Turn left and move onwards to come across a tree, afterwards a barrack and a car. Now turn right and head to the bathrooms or go straight to reach the cistern. To the right of the cistern there's a tunnel and behind it some pillars. The cross-walls can be found between the pillars and rocks. The easiest way is moving clockwise or counter-clockwise and sticking to it. The more pages you have, the more likely Slender Man will be to appear. However it doesn't matter if you're able to collect all of them - the level always ends identically, with Slender Man catching you at some moment.