Aragog was Hagrid's giant spider. He lived in a large cave in the Dark Forest outside Hogwarts. He has hundreds of acromantula children and they, in a shot of the film, were extremely large. His brothers and sisters are evil. They don't attack the school only because of him. In Harry Potter's second year, he and Ron Weasley meet Aragog and are almost killed by him and his family. During the sixth year, Aragog dies, to Hagrid's dismay. Professor Horace Slughorn held an unofficial funeral for Aragog, and entitled him "King of the Acromantulas." Aragog had a wife called Mosag. Aragog lived long enough to become blind before he died. His siblings seized the chance of his death to attack the school in the Battle of Hogwarts, nearly killing Hagrid. The spiders eventually run away to the forest.
Aragog has appeared in 4727 Aragog in the Dark Forest, and 4738 Hagrid's Hut.