While exploring the land around Hogwarts, players may occasionally get a quick glimpse of the giant creature living in the lake around the castle in Hogwarts Legacy. This is only a taste of the rich life that populates the lake, with fans of the Harry Potter movies knowing just how much is down there.
While there are swimming mechanics in the game, players are only given a few winks and nudges about what is happening beneath the surface of the lake, with some of those details being tucked away in side quests. This quest will be given by a Slytherin student who's hanging out down by the boathouse, talking about Merpeople.
Beginning Mer-ky Depths
This quest will appear on your map by the boathouse just outside of the castle's walls. This quest is pretty simple and does not have a recommended level, but it offers a decent reward and more details for those wanting to dive into the lore of Hogwarts Legacy. This quest is given to players by the Slytherin student Nerida Roberts. She aims to create a better relationship between the wizarding world and the Merpeople living within the lake. While no Merpeople themselves are shown, players are able to see a small underwater cave with connections to the Merpeople.
Retrieving The Artifact
Completing this quest can be pretty straightforward, having the player swim nearby to dive into the cave where the artifact is below. While you can swim normally and won't need to go very far, you can fly your broom over to the marked location and get off to fall into the water. It's not a far swim and would only save a few seconds, but with a goblin rebellion going on, every second counts this year at Hogwarts.
Once reaching the location on the map, dive to enter the cave. It will be decently small, with a door on one end with three butterfly slots keeping it locked. The three butterflies are located around the central pool where you entered and can be guided to the door by casting Lumos. Once a butterfly is brought to the door, stop casting Lumos for the butterfly to get on the door. One butterfly will also be behind spider webs, requiring either Incendio or Confringo to burn them away. Only one butterfly can be guided at a time, but the room is small, and this will be a quick process.
After opening the door, there will be a single large chest with the artifact within. Retrieve the artifact and bring it back to Nerida to complete the quest. You can keep the artifact for yourself, but either giving it or keeping it will only affect Nerida's dialogue response and carry no additional weight throughout the game.