The Fifth was an evil tyrant that wanted to destroy Earth and the Nightmare Academy.
The Fifth attacked Earth after the four Named Lords (Slagguron, Tyrannus, Verminion and Barakkas) went to Earth and combined their objects of the Nether. When she got to Earth, she summoned monsters from the Nether by giving people nightmares and then portalling the monsters from the Nether. She then started putting people to sleep by just touching them and sending them to a world she created called the Slumber and then draining people of their energy so that she had enough to summon her Elemental Golems. The Slumber is based on the Nether as it used to be. The only object that could defeat the Fifth was the sword of sacrifice, which only a Double Threat could wield, but no-one has managed to get hold of it before Charlie Benjamin, sacrificing the things most important to his friends to get it. Then he went and after a fierce fight with the Fifth, he defeated her.