Rubeus Hagrid

Hagrid enters the story almost immediately as a mentor-figure to Harry and his friends. In the first book, Rubeus Hagrid is the one who retrieves Harry from his Aunt and Uncle, informs Harry that he is a wizard, gifts Harry with the boy's beloved snowy owl, Hedwig.

Hagrid is a Half-Giant (father is human, mother is giant; Fridwulfa) and gentle as a lamb, unless you insult headmaster Dumbledore in front of him. He always had a love for and a gift for caring for magical creatures, becoming a teacher of the subject in the third book (POA). This love extended to a giant spider (acromantula) named Aragog and countless others. During Hagrid's third year in Hogwarts, Aragog was accused of opening the Chamber of Secrets, resulting in Hagrid's expulsion from the school and his wand being broken. The two halves of his wand are now in a pink umbrella which we saw light a fire and give Dudley a pig tail in Harry Potter and the Sorcerer's Stone. Dumbledore cared for Hagrid after his expulsion, arranged for him to stay on as gamekeeper, and said he would trust Hagrid with his life. In fact, Dumbledore trusted Hagrid with delivering the infant Harry Potter from the ruins of his parents home to his aunt and uncles' home. Hagrid seemed to have owned Sirius Black's flying motorcycle after he was arrested because that's what he used to deliver Harry and to take Harry safely away from his aunt and uncles' home to the Tonks family home in the seventh book (DH).

During Harry's second year (COS) when the chamber of secrets was open, Hagrid was sent to Azkaban because they thought it was him who opened it, just like they thought he opened it during his third year. When Harry defeated Tom Riddle and the Basilisk, he was released because they knew it wasn't Hagrid who opened it. Ron sent the release papers to Azkaban with Errol. This cause them to be delayed because of Errol's old age.

During Harry's third year (POA), Hagrid gets a few hippogriffs to show to his Care of Magical Creatures class. One of them which he grew close to was named Buckbeak and attacked Draco Malfoy in it's defense. This caused Lucius Malfoy to order Buckbeak to be sentenced to death. Buckbeak was eventually saved, however, in order to help save Sirius Black. Harry and Hermione saved Buckbeak by going back in time using Hermione's time turner. Hagrid and Cornelius Fudge thought he escaped on his own, but Dumbledore knew they saved him because it was he who gave Harry and Hermione the idea to go back in time. Sirius Black flew away from Hogwarts into hiding on the back of Buckbeak. Buckbeak eventually became Sirius's because he needed him to stay on the move. In Harry's fifth year (OOTP), we find out that Hagrid has a half-brother who is a giant named Grawp. Hagrid and Grawp grow very close. In Harry's sixth year, Aragog dies and the only people who show up to his funeral are Harry and Professor Slughorn.

Hagrid is the one who carried Dumbledore's body during his funeral. Hagrid serves as a bodyguard for Harry on two occasions (Half-Blood Prince & Deathly Hallows). He barely escaped prison after throwing a "Support Harry Potter" party in the seventh book. He participated in the Battle of Hogwarts, was present when Voldemort killed Harry, and carried Harry's body back to the school before the final battle.