More information can be found on the Slender Man Wiki.
As his name describes, Slender Man is a tall faceless person in a suit. According to the legend, he can stretch out or shorten his arms at will. Depending on various vloggers and bloggers interpretations of the myth, the creature can show a wide range of abilities, ranging from causing memory loss, insomnia, paranoia, coughing fits with or without blood spitting (nicknamed Slendersickness) to triggering photograph/video distortions and statics as well as having teleportation power.
The urban legend became so popular that some games were made as a reference to it, one of which Pewdie played. In this game, which was entitled Slender:The 8 Pages, PewDie has to walk around a forest looking for notes that describe the Slenderman, all this while the creature itself is lurking around, teleporting from one place to another, trying to catch the player.
PewDie encountered Slenderman a few times, and in some cases the screen would go static or a game over screen when he got dangerously close to the creature or vice versa.
At the end of the first episode though, PewDie got so scared he rage quitted the game and googled kitten pictures to calm himself down (see Kitten Therapy). However, he managed to play it again but didn't complete the game. He has made several new attempts, but is always caught by Slenderman as soon as he gets to the 4th note. In this episode he wasn't so scared anymore, and managed to proceed with the note search even when Slenderman is around.
Just a few days later, PewDie played yet another Slenderman related game - this time one of the very first Slenderman games out in the internet. He constantly called it Slendy, short for Slender. He managed to kill it and beat the game in his first try.
He continued playing Slender until July 14; his record was 6 out of 8 pages found.
On July 16, 2012 it was CutiePie's turn to play it. She was able to find 4 pages before being caught by Slenderman.
PewDiePie then began playing Slender Mod. A mod of the original Slender. Pewdie managed to collect 7/8 pages. So far he haven't played the mod again Barrels A mod was created for Slender called Barrels. PewDie played the mod on August 26, 2012.
Slender Man's Shadow
On August 17, 2012, a new Slender game came out known as Sanatorium, which is based on the game Slender. PewDie manages to collect 5 of 8 pages. In Sanitorium, it is revealed that the Slenderman also moves by "moonwalking," besides "teleporting static."
The next day, PewDie has a new Slender record of 7 out of 8 pages, just needing one more to win the Sanatorium map.
On August 24, 2012, Part 2 of what started with Sanatorium, Hospice was released.
PewDie had 8 glowsticks and collected 6 of 8 notes before getting killed by Slendy.
The next map by the creators was titled Elementary. It was released on August 31, 2012
PewDie did not play/has not yet played Elementary.
Another map in the Slenderman's Shadow series, the goal was to collect 12 mementos.
PewDie collected 9/12 in his 1st attempt, 6/12 in his second.
He collected 12/12 in his 3rd and managed to get out safely, dancing to the music in pure happiness.
This is the first Slender game PewDie has ever completed.
PewDie did not play/has not yet played Claustrophobia
PewDie did not play/has not yet played 7th Street.
PewDie did not play/has not yet played Prison.
PewDie did not play/has not yet played Carnival.
Haunt: The Real Slender
A different Slender Man game. In this game, Pewdie walked through a park while avoiding Mark Slender, an alternate version of Slender Man (who Pewds thought was Slender Man due to the fact that he hadn't found enough story notes) with little to no effort. Pewdie found a few different pages scattered through the park, and complimented how the game had actual story to it. In the end, Pewdie tried to watch Frankenstein on a TV, only to get caught by Mark Slender. So far he haven't played it again.
Another Slender Man game with an actual story. In this game, Pewdie starts out in the forest, as usual. He then comes across a note in a house that tells him to go to an underground facility, but Slendy is in hot pursuit. Slendy catches Pewdie on his first attempt to reach the facility, but succeeds on his second try. After activating a generator in the facility and finding a note, he encounters Slender Man again, but escapes. On his way, Pewdie finds a sign that points in two directions. He does his usual "Ole, Dole, Doff..." to make a decision, only for Slender Man to kill him as soon as he finishes, thus ending the first episode of Slender Woods. In the second episode, Pewdie meets up with Jennifer, only to get caught by Slender Man. After multiple encounters with Slender Man, he finds a gun and proceeds to shoot Slendy three times. PewDie then attempts to escape the forest, only to get surrounded by multiple Slender Men.
Slender: The Arrival (BETA)
The beta for the full version of Slender: The Arrival was recently played by PewDiePie. It offers much improved graphics, and serves as a remake of the original; the full version of The Arrival will include a story mode and more levels, with more than just one enemy.
This is the first official Slender title that PewDiePie has ever succeeded in completing, even though technically he really hasn't completed it yet since all he beat was the beta.
Slender:The ArrivalThe full version of Slender: The Arrival, which was recently released and played by PewDiePie. It features a new character: The Chaser, a woman once known as Kate, but now turned into a proxy for Slender Man. PewDiePie nicknamed her 'Slender Woman'.
- A more recent game (by the creators of the original "Slender" game) has been created and played by PewDiePie.
- A character in both Mad Father& Misao is also named Slenderman by PewDiePie.