The Sorting Hat

Created thousands of years ago, the sorting hat has sorted every student who has ever entered Hogwarts into one of four houses: Ravenclaw, Hufflepuff, Gryffindor, and Slytherin.

It does this by looking through the student's minds and thought processes, and talking with the student to determine which house is the best for them. Supposedly, it can break through all occlumency, no matter how strong, and the only thing he has been unable to see is the memories in Ron's mind which the Entity protects.

The hat is also bound by magic to not reveal a student's secret, unless that student, or other students, are in danger. The hat will also defy anyone, including the headmasters and teachers, to help his students in Hogwarts. Several times he has refused the demands of the headmasters over the years, including Albus Dumbledore.

The sorting hat also often contacted Ronald during his times at hogwarts to help him, as he promised.