In the Shadow of the Undercroft is the twentieth main quest in Hogwarts Legacy. This walkthrough will guide you through all objectives of the In the Shadow of the Undercroft Main Mission.
Requirement: having completed Flying Class, Level 8
Reward: 260 XP, Confringo
Quest Info: Sebastian showed me a hidden room called ‘the Undercroft’ where we could talk printed. I finally told him the truth about my ability to see traces of ancient magic. In return, Sebastian taught me the Blasting Curse, Confringo. The Undercroft is a great place to practice spells; I can see why Sebastian wants to keep it a secret.
Objectives:
- Meet Sebastian
- Enter the Secret Room
- Explore the Room
- Talk to Sebastian
- Practice Casting Confringo
- Check Back with Sebastian
- Leave the Undercroft
Starting Location: In the Shadow of the Undercroft
We can now fly a broomstick. After our first flying class, Sebastian wants to meet with us.
Meet Sebastian
Warp to Defense Against the Dark Arts floo flame in the Astronomy Wing and then proceed to the quest marker to speak with Sebastian.
Enter the Secret Room
Follow Sebastian to the back of the hall and hold 
/ 
to open the secret passage to the Undercroft.
Explore the Room
When you enter the room, use Revelio to reveal the location of some chests. Open them all and then walk up to Sebastian.
Talk to Sebastian
Talk to Sebastian and you will then learn Confringo, the Blasting Curse. As usual, steady your wand with the left stuck and guide it along the symbol’s path to learn the spell. Don’t let go of the left stick and remember to press the corresponding button to gain speed and lose the red spark.
Practice Casting Confringo
The Blasting Curse, Confringo, fires an explosive blast. It’s particularly useful if you want to set enemies on fire from afar and to solve certain environmental puzzles around the world, specifically Merlin Trials. Practice it on the ceiling candelabra marked by the yellow waypoint. First, equip Confringo in your Spell Set and then press 
/ 
to lock on the candelabra. Then, cast it using 
plus the chosen spell slot Once you’ve lit a candelabra, repeat the same on all candelabras in the room.
Check Back with Sebastian
Now return to Sebastian to get him up to speed with your recent findings.
Leave the Undercroft
Now leave the Undercroft and you’ll meet Ominis outside. Choose any dialogue option you want.
This finishes In the Shadow of the Undercroft in Hogwarts Legacy.
Next Quest: The Room of Requirement
For all other quests refer to the Hogwarts Legacy Walkthrough.
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