House Ghost, The Grey Lady:
Ravenclaw House appears to have little rivalry with the other houses, except in Quidditch. Harry Potter believed that they tended to side with Gryffindor in its rivalry with Slytherin, as did Hufflepuff house. However, during the 1994 Triwizard Tournament, most Ravenclaws supported Hufflepuff Champion Cedric Diggory over Harry. They believed that Harry had in fact cheated his way into being a champion and that the true Hogwarts champion was Cedric. Many Ravenclaws (such as Cho Chang) joined Dumbledore’s Army and fought in the Battle of Hogwarts along with Gryffindors and Hufflepuffs. They rose at almost the exact moment as the Hufflepuffs and turned their wands upon Pansy Parkinson and Slytherin House in Harry Potter’s defence, when the former wished to hand Harry over to Lord Voldemort and his army of Death Eaters.
Within the house, though, they’re well-known for being welcoming and encouraging of creativity, eccentricity and individuality and being very accepting.
Common Room:
The Ravenclaw common room is in one of the castle’s towers and is wide and circular. You have to climb a tight spiral staircase to get there. It has graceful arched windows, and the walls are hung with blue and bronze silks. The domed ceiling is painted with stars, which are echoed in the midnight-blue carpet. Tables, chairs, and bookcases cover the expanse of the floor, and a white-marble statue of Rowena Ravenclaw sits next to the door that leads to the dormitories above. Harry Potter entered the common room in 1998 while searching for clues to the location of one of Voldemort’s Horcruxes.
Unlike the other common rooms in the school, a logical riddle given by a bronze eagle-shaped knocker must be answered to enter. This could prove troublesome as anyone with enough intellect could intrude into the dormitory, as is shown in 1998 where Professor McGonagall had no trouble entering by answering the riddle correctly (though she was a “hatstall” between Gryffindor and Ravenclaw). However, Hermione stated in her first year when figuring out the complicated riddle, beneath the trapdoor, that most wizards and witches do not have much sense of logic, which might be something that Ravenclaw noticed herself and decided to use clever riddles instead of passwords, as they are safer than some words.
Authoritative and comprehensive information about Ravenclaw is found on the Pottermore site.