Harry Potter and the Chamber of Secrets

Here the main colours used are green and black; these are the Slytherin house colours, famous for: 

• Evil Wizards/Witches
• Voldemort
• Cunning/Sly students

This gives the audience that something scary and evil is about to come face-to-face with the three characters pictured; the slogan 'Something evil has returned to Hogwarts' tells us that this is not the first time; nor will it probably be the last. Suggesting that for this thing to have entered the school more than once it is just as powerful if not more so than the headmaster Dumbledore himself; this is a critical question throughout the series. Also the fact that it is capitalized and exclaimed tells us that it must be very hard for something evil to enter Hogwarts; this could tell us that it is extremely strong and ruthless.

Dobby, the house elf tells us that the evil power comes from someone who is rich/wealthy enough to own a house elf; this could also tell us that he does not believe in equal rights - which of course we know he doesn't as he tried to kill all the 'mudbloods'.
The fact that Harry bears a sword tells us that he will come face to face with the 'baddie' in this film, which reflects the looks of horror upon Hermione and Ron's faces. Suggesting that Harry, Hermione and Ron will have to be brave and courageous, which links to the traits of their Hogwarts house, Gryffindor.
Overall i think it is a successful poster, as it promises action and mystery; there is already a huge fan base for the film series so no matter what it looks like it was going to be seen as successful.

Amy