Meeting at the Astronomy Tower | Walkthrough HP and the HB Prince Guide
Last update: Wednesday, May 11, 2016
Head to the Training Grounds and to the door  leading to the Astronomy Tower. Go through it and take the stairs  up.
Turn right on the fork and go down the stairs . This path will lead you to the library .
Once you enter it, Draco's friends will appear . You have to fight with each of them .
After the fight's over, smash the key against the wall and pull it through the bars . Afterwards repair it with Reparo and put into the mechanism .