Slytherins

Slytherins tend to be ambitious, cunning, and achievement-oriented. They also have highly developed senses of self-preservation. This means that Slytherins tend to hesitate before acting, so as to weigh all possible outcomes of a decision (and how these outcomes would personally impact them), unlike Gryffindors, whose chivalrous natures would likely lead them to react immediately and instinctively.

According to Albus Dumbledore, the qualities which Salazar valued in the students he chose included cleverness, resourcefulness, determination, and "a certain disregard for the rules." Dumbledore noted that all of these were qualities possessed by Harry Potter, who was in Gryffindor.

The Sorting Hat claims that blood purity is a factor in selecting Slytherins. This suggests that it bases its decisions more upon the views of its members than on any accurate test of a student's lineage. Muggle-born Slytherins exist, but are very rare, as noted insultingly by Scabior the Snatcher. There have also been definite examples of half-bloods sorted into the house, including Tom Marvolo Riddle and Severus Snape. Harry Potter was nearly sorted into Slytherin, but ended up in Gryffindor instead.

Contrary to the wishes of the other founders of Hogwarts, Salazar Slytherin wanted a stricter policy of admission to the school - one limited strictly to pure-blood students. The controversy this created apparently led to Salazar leaving the school and the Chamber of Secrets behind. A millennium later, the house's students are still considered affiliated with Salazar's reputed views, and open expression of pro-blood purity sentiment does seem to be more common in Slytherin than in other Houses.

Members of Slytherin:

* Tom Marvolo Riddle
* Severus Snape
* Lucius Malfoy
* Draco Malfoy
* Vincent Crabbe
* Gregory Goyle
* Pansy Parkinson
* Marcus Flint
* Blaise Zabini
* Phineas Nigellus Black
* Regulus Black
* Horace Slughorn
* Andromeda Tonks
* Black family

Credit: Harry Potter Wiki