You’re using the Expecto Patronum spell here. When fighting Dementors you can’t move forward or backwards. You want to keep moving around left to right in your circle and always cast the closest one. It’s a bit like whack-a-mole or one of those games where something pops out. Just keep looking and casting who ever is closest not the first one you see. This time it doesn’t work in your favor to keep the left mouse button, spell casting, held down because it will track on the next dementor who may not be closest. After the short practice turn left, turn right, enter room on the left. Cast the skull and armor and go out the last exit on the right. Go straight across, cast skull and trunk. Go out and turn right. Cast skull on the left go down stairs to the save book. Walk forward to case and a boggart comes out. Defeat him and 2 more will appear. Defeat them for Famous Witches 3 card. Hit a trap door. 3 boggarts will appear. Defeat them and reach a cut scene.

The Library

You’re attacked by 3 waves of books. Move quickly while holding down the spell cast button. Cast the bulb in the center of the ceiling, land on the table, cast the next bulb. Go all the way to the left and cast the trunk, Famous Wizard 13. Go straight all the way back around to the right, cast the bulb to release the bookcase stairway. As Hermione, climb up, cast locks until Ron joins. Go in and left to save book. Cast picture on the left for a gargoyle to appear. Cast the gargoyle for a secret spot in the books. Go in and right. You’re attacked by imps, defeat, cast dragon on the left. As the Dragon, turn left, turn right, turn right, in the room blow fire on the fire place on the left, cut scene shows a wall opening. Return as Hermione, go down hall, cast trunk on the left. Go back to the fireplace, room opens, cast trunk on left. On the way walk to the book. Cut scene. Go left to class into the new room.

Charms Class

When dealing with Salamanders, make sure you destroy the fire quickly or it will create new salamanders. If you can cast the Salamander twice quickly then do. If not take out the flame and then go after him. He will throw fire at you but they move so slowly you can avoid it fairly easily. Go straight to cast the salamander and then cast the fire. Get Shield 1. Turn left and on the left cast the banner, secret area 1. Climb in and cast the trunk, Famous Goblins 1 card. Leave turn left.

Harry Potter and the Prisoner of Azkaban Walkthrough