Hogwarts Legacy is chock-full of side quests that immerse you further into the magical world of witchcraft and wizardry. You can usually unlock them if you talk to your fellow students or other NPCs with a distinct marking above their heads.
One of the side quests that will help you explore the Black Lake area some more comes from a Slytherin girl called Nerida Roberts. In this guide, you can learn how to complete the “Mer-Ky Depths” side quest in Hogwarts Legacy and help build better diplomatic relations with the Merpeople!
How to start the “Mer-Ky Depths” side quest in Hogwarts Legacy
You can find Nerida sitting on the docks at the Hogwarts boathouse, ruminating on how to get to the underwater cave where Merpeople left her a gift in return for the one she gave them. The problem is that she can’t swim, so she asks you for help once you talk to her.
This side quest requires you to reach Level 10, but it becomes available after you complete the main quest called Percival Rackham’s Trial.
How to complete the “Mer-Ky Depths” side quest in Hogwarts Legacy
After you exhaust all dialogue options with Nerida, head to the quest marker in the water close to the cliffs. You can swim there or jump on a broom and fly this short distance. At the marker, you will see a small whirlpool that allows you to dive if you press and hold the square button on your PS5 controller (or the equivalent for Xbox and PC).
You will surface in a small cave with a sealed-off chamber with three empty moth slots on the door. By now, you may have solved a few puzzles around the castle that involve moths, so this one may look familiar.
The goal is to explore the area surrounding the pool and retrieve moths to unlock the door. You can find the first moth next to the pool opposite the door. Approach it and cast Lumos to attract the moth, then carry it to the door and extinguish the light.
The other two moths are in the small alcoves to the left and right, but first you need to clear out some cobwebs using Incendio. Once you do, bring the remaining two moths to the door by casting Lumos again.
The door will open, and you will need to collect a Mermish artifact and bring it back to Nerida to complete the quest. In return, you will receive the Mermish Liaison Uniform and 180 XP.
We hope you have fun completing this side quest! If you need more help, make sure to explore our other Hogwarts Legacy articles.