The Shadows of the Undercroft is a main story quest in Hogwarts Legacy. During this quest, you will visit Sebastian, who is not in his usual spot, as he wants you to meet him somewhere special. If you get his OWL, and track the quest, you will head over to the Dark Arts tower, and meet him near a flight of stairs. Here you will get the quest, the Shadows of the Undercroft, and learn to cast the Confringo Spell.

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Here is a walkthrough to the Shadows in the Undercroft quest in Hogwarts Legacy.

Hogwarts Legacy: Shadows of the Undercroft¶

When you start the quest, follow Sebastian behind a flight of stairs, to a strange contraption in the corner of the corridor. This will allow you to enter a secret room, called the Undercroft. In this room, Sebastian will teach you the ways of the Confringo spell, a powerful combat spell, which launches a fireball at a distance towards your target.

When you get the spell, Sebastian will task you with lighting three braziers on the roof. Place the spell on your hotbar, then cast it at each of the three braziers. Once you light all three braziers up, you will complete the main bulk of the mission.

Before you leave the Undercroft, make sure to loot the area. A few bags and chests are knocking around the room’s sides, which can give you some extra money and gear before heading off.

Shadows of the Undercroft: Best Choice¶

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Will you rat Sebastian out, or will you not?

Ominous Gaunt Dialogue Choices¶

Now that you leave the Undercroft, Sebastian’s friend, Ominous Gaunt, will be standing there, waiting for you to leave. At first, he doesn’t recognize you, but he soon figures out you’re not Sebastian. Instead, he hounds you, asking how you know about the place. You can answer the following ways:

• Sebastian showed me.
• I stumbled upon it.

If you grass Sebastian up, Ominous will be angry he shared their secret with someone else. And if you lie to him by saying you found it, he will be able to tell you’re lying and know Sebastian showed you. So, choosing whoever one doesn’t really matter.

After that, you get another dialogue option about keeping it a secret.

• I promise not to say anything
• No need for threats

Selecting not to promise to say anything will result in you promising, and then saying, don’t be too quick to judge his oldest friend. If you choose the threat option, you will say don’t worry mate you’re cool, and then don’t worry about Sebastian. Both answers will result in him saying don’t lecture him about Ominous’ oldest friend at some point. And, at the end of the conversation, Ominous walks off saying aloud that Sebastian is going to get an earful.

So, no matter which answers you choose, you will essentially get a different dialogue option, but the outcome is always the same. You can either be nice, friendly, and reasonable about it. Or, you can be an arse back to him. It’s your call.