"and Slytherin took only those with cunning, just like him."

-The Sorting Hat

       Slytherin, out of all the houses, probably has the worst and most unfair reputation. Although it most certainly produces the most dark wizards, that doesn't necessarily mean that all of them are bad (personally, I have a friend whose a Slytherin, and I'm in Gryffindor). If you want to know more about this secretive house, then this is the right chapter for you to read.

       The Common Room:

       The location of the Slytherin common room's secret entrance can be found in the dungeons, through a corridor ending at a stone wall. Like Gryffindor, in order to enter, you need a pass-phrase. Once you speak it, the wall should slide aside and allow you passage through. The common room is full of green light, as it is under the lake. There are many black armchairs and skulls lining the walls, as well as a fireplace to your left, and the floor and ceiling are made of stone. The leader of this house is the Potions teacher, who hardly ever visits.

       The Symbolization:

       The qualities of this house, I believe, are also quite unclear in the Harry Potter books. The first one that Salazar looked for was ambition (a desire to do great things and have many achievements). If you think about it, this is actually a good quality to have whether you're in Slytherin or not. The second, which most people have come to despise, is pure blood. Just because its one of the qualities that their founder looked for doesn't mean that all Slytherins feel this way (my Slytherin friend is actually quite pleasant). The symbol of this house is a serpent because their founder, Salazar Slytherin, was a parselmouth, meaning that he could talk to snakes. This is actually part of the reason why it is considered a dark art. To be fair, if people didn't contribute to this houses terrible reputation (Slytherins included), it might not be considered that way at all.

"Great ambition is what this place needs, and is what makes a person famous and important."

-Slytherin prefect, Pottermore.com