You will visit the clock tower on multiple occations during your adventures in Hogwarts Castle. Your first visit will be during the dueling club challenges. When you are here, you are sure to notice there is a small door in the corner that keeps slamming shut before slowly opening again. The door has a picture of a unicorn on it but there isn’t an obvious way to open it and no spell that seems to have any impact on it.
There are actually four of these doors in this tower and the method of opening them is the same. The solution is pretty simple, here is what you need to do to be able to fully open the door with the metal unicorn cage on it that is slamming shut in the clock tower.
Opening The Unicorn Cage Door
The secret is with the pendulum that is swinging. If you look along the floor, there are four different icons. On the far side of the room, along the pendulum’s path, you will see an icon of the unicorn. If you look back at the cage door, you will see it begins to open up every time the pendulum passes over the icon of the unicorn.
The solution is to make the pendulum stay longer above the desired icon, in this case, the Unicorn, so that the metal cage will open up. The solution is to use the Arresto Momentum spell. When the pendulum is over the icon of the door you are trying to open, cast the spell on it to freeze it in place. This will give you enough time for the door to unlock and allow you to go inside.
This video guide will explain the process to you in better detail and will show you how to unlock the unicorn door along with the three other metal cage doors in this room.