Hogwarts Legacy In The Shadow Of The Undercroft is the second main quest in the fifth chapter of the video game published by Warner Bros Games, and it revolves around a new secret room youβll get the chance to find with the help of Sebastian.
In The Shadow Of The Undercroft quest in Hogwarts Legacy is relatively short as it is based on a series of dialogues and decisions, but itβs a mandatory part of the story. Besides the fact that youβll progress the story and earn 260 XP by playing this quest, youβll also unlock Confringo or one of the Spells available in Hogwarts Legacy.
Where To Find Sebastian
Since In The Shadow Of The Undercroft main quest is triggered after you finish the Flying Class main quest, the first thing youβll have to do is to find Sebastian. Open the map in your Field Guide and track the current quest. Remember that The Room of Requirement is also available now, but first, weβll deal with Sebastian.
Youβll find him in The Astronomy Wing, close to the Defence Against The Dark Arts Classroom Floo Flame. If you have unlocked the said Floo Flame, fast-travel to it. If not, while tracking the current quest, press Up on your DPad and follow the path on the minimap or the golden whisps that spawn. Sebastian will be waiting for you at the bottom of the stairs leading to the Defence Against The Dark Arts Classroom.

In The Shadow Of The Undercroft Secret Room
Talk to Sebastian Sallow, and heβll tell you he has something to show you. As you remember, the last time you saw him was in the Library Restricted Section, where he took the fall for you as part of the Secrets of the Restricted Section main quest.
Since the topic you are about to discuss is quite private, Sebastian suggests itβs better to find a better spot to share your findings with himβspecifically the Undercroft Secret Room.
The Hogwarts Legacy Undercroft Secret Room is relatively easy to find since itβs at the end of the corridor behind Sebastian. To get inside, start by following Sebastian, then interact with the large clock around the corner to open a secret passage.

Undercroft Secret Room Chest Locations
After you get inside, take your time to explore the room because there are 3 Treasure Chests to be found:
- One Treasure Chest is located on the right side as you enter, close to the wall behind Sebastian
- The second one is in the back of the room by some barrels
- The last Chest is by a stone pillar near the center of the room
Loot all three of them, then talk to Sebastian, and youβll mention Ominis, a blind student and a member of the Slytherin House.
Sebastian will explain that itβs quite unusual that Ominis can use his wand to navigate since he was born blind. Furthermore, heβll explain that Ominis knows about this chamber since he was the one who discovered it after being mentioned by one of his family members.
Sebastian also insists on not sharing the location of the Undercroft Room with anyone, especially Ominis, because he is not proud of his family. If you want to know why, Sebastian will explain that Ominisβ family were direct descendants of the Salazar Slytherin, obsessed with their pure blood heritage. Because of this, Ominis hates them.
Now Sebastian will explain that the Undercroft Secret Room is perfect for practicing Forbidden Spells such as the Blasting Curse he is about to teach you. Now youβll have two dialogue choices:
- Thatβs ridiculous.
- It does sound dangerous.
Pick the one you want because Sebastian will still teach you the spell, and the choice you make here will not affect the story.
Now, get ready to unlock Confringo by completing the associated mini-game. As you probably know by now, youβll have to guide your wand (blue arrow) as fast as possible, following the pattern on the right side while pressing the buttons on the pattern when your wand is above them.

Great job! But now itβs time to practice it.
How To Practise Casting Confringo
To practice casting Confringo and complete the next objective of the Hogwarts Legacy In The Shadow Of The Undercroft, you must set on fire several chandeliers. So start by equipping your spell (press Right on your DPad), then check the ceiling to spot the suspended braziers.
Aim by pressing the Right Thumbstick, then cast Confringo to set the braziers on fire.

After you cast Confringo on all braziers, the practice ends, so return to Sebastian. While discussing the Confringo Spell, again, youβll have two dialogue choices:
- Itβs almost too much.
- Iβm ready for more spells like this.
Again, pick the one you want since there are no penalties, and Sebastian will mention his sister, Anne. Tell him you would be glad to meet her, even though your choice wonβt change anything. But since he took the blame in the Library, visiting Anne is the least you can do.
Now itβs time to share with Sebastian everything that happened and tell him about your ability to use Ancient Magic. Feel free to keep some of the secrets to yourself, but know that nothing will change in the game if you tell Sebastian your story. After you share your story with Sebastian, itβs time to exit the Undercroft, so head through the marked door. On your way out, youβll meet Ominis.
Unlike Sebastian, Ominis is not as friendly, and it is actually quite similar to Draco Malfoy, but unlike the letter, Ominis hates his family and his house. During the conversation with Ominis, heβll ask you how did you find the Secret Room, and youβll get two choices:
- Sebastian showed me.
- I stumbled upon it.
Whatever you choose here, Ominis will know Sebastian was involved, so feel free to pick the choice you consider fit. Finally, Ominis will tell you not to tell anyone about the Secret Room.
Although his threats donβt mean anything, promise him you wonβt say anything. It is the least you can do for someone who already suffers. Finally, step away from Ominis, and the Hogwarts Legacy In The Shadow Of The Undercroft ends, but now is time to find another secret room by playing the next quest named The Room of Requirement.