When Hagrid was a young man attending Hogwarts, he was given an egg by a traveler, which later hatched into an arachnid, who he then named Aragog. Hagrid kept Aragog safe in the dungeons at Hogwarts, where he would feed and visit him. Tom Riddle ended up finding Aragog, and framing him as being the monster who opened the Chamber of Secrets. Hagrid then helped Aragog escape into the Forbidden Forest, and Hagrid was later expelled from Hogwarts.
Aragog’s loyalty lies only with Rubeus Hagrid, and although he wasn’t the monster in the Chamber of Secrets, his instincts are to eat humans. Aragog is a part of the Acromantula colony, which is headed by his wife Mosag. Aragog is the size of a small elephant, and has 18 ft leg span. It is quite ironic that Riddle accused Aragog for being the monster in the chambers, because all spiders fear the real monster, the Basilisk.
Even though most people still believed Hagrid opened the Chamber of Secrets, Albus Dumbledore, knowing Hagrid was innocent, hired Hagrid to be gamekeeper at Hogwarts. Years later, while Harry Potter attended his 2nd year at Hogwarts, the Chamber of Secrets was opened once more. With the re-opening of the Chamber of Secrets, several students were stunned, and Hagrid was sent to Azkaban to keep him from doing further harm. Before Hagrid was sent away, his final words were:
“If, uh, if anybody was looking for some stuff, then all they'd have to do would be to follow the spiders. Yup. That would lead 'em right. That's all I have to say.”
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