Hogwarts Secrets

To complete this puzzle you must learn the Glacius (imo the best) or alternatively Arresto Momentum spell. There are 4 doors in the tower, and there is a symbol on each of them. To solve the puzzle you have to open them and you will be able to do it when you use spells to stop the clock's pendulum so that it covers the same symbol as on the door.

At the lowest level of the tower there is a door with a unicorn symbol,...

...so you should stop the pendulum in the position as shown in the picture below.

The next door is located a level above.

To get to the next door you need to go even higher.

To get to the last door you must, while on the same platform as for the third door, freeze the pendulum in the right position...

...and quickly run up the staircase a floor above and go to the side room.

To complete this puzzle you simply have to find the key that will allow you to open the door located at the end of the corridor. The key that will allow you to open this door is located in the Headmaster's office.

The necessary condition to open the door to the room with the key is to have the Alohomora spell that allows you to open level 3 locks.

You can get to the door of the room where the key is in two ways:

You can follow the main storyline of the game until you reach the quest "Niamh Fitzgerald's Trial" in which you visit the Headmaster's office (or later). You must then unlock the door leading outside (Level 2 Lock) to the balcony with the staircase and then take the stairs up and unlock (Level 3 Lock) the door to the room with the key.

If you want, you can also do this much earlier, you just need to have a broomstick. You just need to land on the balcony of the Headmaster's office balcony (I don't know if this is an intended possibility so it may be "fixed" in one of the future updates).

Look at the circular manhole located at one end of the bridge. There are four symbols on it and next to them are Roman numbers I, II, III and IV.

To open the manhole and be able to get under the bridge you must first use a fire spell, such as Confringo to light the four braziers located at both ends of the bridge.

There is a symbol located below each of the braziers, one of the four that were also on the manhole. When the braziers are burning you can rotate them and thus change the number. Set the number next to each brazier to match the number on the manhole, so for example, for the symbol that looks like a square it would be IV. If you set all four braziers correctly, the manhole will open.