Harry Potter: The Philosopher's Stone & The Chamber of Secrets

Explanation: Fluffy belongs to Hagrid, who bought him "from a Greek chap". He falls asleep to music, that's how Harry, Ron and Hermione get past him using an enchanted flute.

Explanation: Nicolas Flamel is a real French alchemist (1330-1418) that J.K. Rowling weaves into the HP universe. In the books, he is 665 years old and willingly destroys the Stone at the end of Book 1 so it doesn't fall into the wrong hands.

Explanation: The Mirror of Erised ("Desire" reversed). The inscription on the frame is also reversed. Harry sees his dead parents in it; Ron sees himself as Quidditch captain and Head Boy.

Explanation: Professor Quirrell, who teaches Defence Against the Dark Arts, has been sharing his body with Voldemort for months. His purple turban hides Voldemort's face attached to the back of his skull.

Explanation: The Ollivander family has been making wands since 382 BC. Garrick Ollivander tells Harry: "The wand chooses the wizard." He remembers every single wand he has ever sold.

Explanation: Devil's Snare. It's the first protection after Fluffy. Hermione remembers Professor Sprout's lesson: fire or light makes it recoil.

Explanation: Tom Riddle's diary, a Horcrux, though we don't learn that concept until Book 6. Lucius Malfoy planted it in her cauldron to reopen the Chamber of Secrets.

Explanation: Aragog is an Acromantula, a giant talking spider. Hagrid raised her in secret at Hogwarts as a student, which led to him being falsely accused of opening the Chamber of Secrets.

Explanation: Polyjuice Potion. It takes a month to prepare and requires a fragment of the other person (hair, nail). Hermione, Ron, and Harry use it to infiltrate the Slytherin common room as Crabbe, Goyle, and... a cat (Hermione botches it).

Explanation: Gilderoy Lockhart, famous for his autobiographies. It turns out he actually stole other wizards' feats and then wiped their memories. He ends up at St Mungo's after botching a Memory Charm on himself.

Explanation: The Sword of Gryffindor, which Harry pulls from the Sorting Hat, only a true Gryffindor can do this. Forged by goblins, the sword only takes in what makes it stronger, like Basilisk venom.

Explanation: Fawkes, Dumbledore's phoenix, weeps his tears onto the wound. Phoenix tears are the only known antidote to Basilisk venom, without them, Harry would have died within minutes.

Explanation: Moaning Myrtle, who was killed at age 14 by the Basilisk's gaze during the first opening of the Chamber by Tom Riddle 50 years earlier. Her sink is also the entrance to the Chamber of Secrets.

Explanation: A sock. Harry hides one of his socks inside the diary he returns to Lucius, who unknowingly hands it to Dobby. A piece of clothing given by a master automatically frees a house-elf.

Explanation: Tom Riddle as a Hogwarts student, young Voldemort. He was Head Boy in Slytherin, released the Basilisk, killed Myrtle, then framed Hagrid before being celebrated for "solving" the case.