Go to Hagrid's hut

Your first stop should be to visit Hagrid. As an expert on the Hogwarts grounds and the Forbidden Forest, he should be able to tell you where to start looking, even if he doesn’t know where particular plants grow. There’s also a chance that he’ll have one of the more difficult potion ingredients, which would make your job much easier.

The path to Hagrid’s hut winds down from the castle and along the shore of the Great Lake, before heading towards the forest. As you walk down to the lake, you take in the view. The Great Lake is a mass of darkness. The water is smooth with barely a ripple, reflecting the pinpoints of lights in the sky above. If you turn, you can see the silhouette of Hogwarts castle, its windows like constellations in their own right.

Just as you reach the lake, you hear a quiet splash. You look over the lake and see concentric circles ripple over the surface of the water. You hurry onwards, but before you get far, you hear another splash. This one is louder and sounds much closer. You glance again at the lake and notice an arrow of ripples moving purposefully towards you. To your left, a steep bank stops you from moving away; instead you begin to run. Your instincts scream that you’re being chased.

You give yourself one look back and your fears are confirmed. Rising out of the water is a mass of tentacles. They speed towards you faster than you can run. You try to jump out of the way, but manage to trip over a stone instead. You stumble out of control towards the lake, with the tentacles reaching you just as you hit the surface.

You are dragged below the water. You’re so wrapped in tentacles that you can’t reach your wand. You hope that the giant squid doesn’t see you as a meal – or as something else – but you don’t know how to get out of this mess.

Luckily, help is on its way. Just as you’re beginning to black out, the squid jerks back and releases you. You see a trident sticking into its flesh. One large eye stares at you for a moment before the squid retreats back into the deep. You’re still out of breath and too far from the surface to make it in time.

That’s when your rescuers swim into view. You should have expected them to be merpeople, since you’ve met them before in the lake. The leader of this pack swims towards you. You’re worried that he’s about to attack you, but you don’t have any energy to repel him, anyway. Instead, he places his lips against yours and breathes into you. Your lungs fill with air, giving you a few more seconds before you pass out.

Quickly, you take out your wand. The merman shoots back and the rest of his pack circle you, their tridents pointing at you. It’s clear they’re scared of what you could do. Attacking the merpeople isn’t your intention, though. You move your wand in the necessary arc and concentrate on the charm you need. To your relief, a jet of air is expelled from the tip of your wand and forms a bubble around your mouth and nose. Gratefully, you breathe in.

You remember that you’re surrounded by a circle of angry merpeople. Carefully, you slide your wand back into your pocket and raise your hands into the air. The merman who saved you approaches you again.

“Who are you?” he asks, his voice melodious in the water. “What do you want with us?”