In The Shadow of the Undercroft is one of Sebastian’s questlines in Hogwarts Legacy. You will get to complete this quest early on in the game and is where Sebastian teaches you how to cast Confringo, a blasting spell.
Confringo is a long-ranged fire spell that is perfect against ranged enemies. You are going to be using Confringo a lot throughout the game, so make sure to add it to your hot bar for quick-casting.
You will unlock In The Shadow of the Undercroft right after learning how to fly a broom in your Flying Class.
In the Shadow of the Undercroft walkthrough
To thank Sebastian for his services, you need to visit him at the Defense Against The Dark Arts Tower in Astronomy. After the meeting, he will lead you to a secret entrance which will be at the end of the dead-end corridor.
The secret entrance is a direct passage to the Undercroft and can be opened by interacting with the cabinet.
After getting inside Sebastien’s secret location Undercroft, you can wander around to find multiple Collection Chests. You then need to start a conversation with Sebastian.
Learn Confringo
In Hogwarts Legacy, there is a Blasting Curse known as Confringo and Sebastian will teach you that. Soon after talking to him, a symbol will appear on the screen.
To learn Confringo, you need to trace the symbol with your wand which can be controlled with the left stick. The trick of the trade while learning new skills is to never let go of the left stick.
Notice on the screen if the wand is slow or has a red spark behind it and correct it by pressing the right button on the console. After learning the skill in the minigame, you can proceed to practice.
There are three chandeliers in the room that can be lit up using your new skill. After locking Confringo by pressing R3, use the R2 to cast it on the chandeliers.
Leave the Undercroft
After the practice, you need to return to Sebastien and tell him about the newly learned skills. After this conversation, you are free to go out of the Undercroft. Heading out of the Undercroft will conclude In The Shadow of the Undercroft.
