Arachne is the immortal and now goddess of weaving. Although she was a mortal, her side effect was that she would be turned into a spider by Athena, who will spin colorless thread for eternity. Although, Athena and her children (such as Annabeth) have a great fear of spiders but they try hard to conceal it.
Arachne is vicious and she does not have the heart to forgive. Arachne is thirsty for revenge, such as the time when she sent Annabeth and Percy down a hole to the Underworld.