Aragog

Aragog was a blind Acromantula owned by Rubeus Hagrid. Like the rest of his species, Aragog had a taste for human flesh and was able to communicate with humans. In his youth he was the size of a Pekingese and near the end of his life was about the size of a small elephant. Aragog had a wife, Mosag, and was the leader of a large Acromantula colony composed of all of his sons and daughters. During his life, Aragog was accused of being Slytherin's Monster, although this was really a basilisk. Ironically, all spiders fear the basilisk. After the Acromantula died, some of his venom was taken by Horace Slughorn and was most likely sold later on.