Straight out of the Bible. He will rise during the Apocalypse and cause general disarray. Revelation Ch.12: "There was a gigantic fiery-red dragon with seven heads and ten horns and on his heads seven diadems. His tail swept away a third of the stars of heaven and hurled them to the ground."
While he waits for the end of the world, the Dragon lives in Hell, reading Anne McCaffrey novels. Or, rather, six of his heads do. Areth, Ukath, Koth, Helleth, Semmoth and Enkith believe the "Dragonriders of Pern" series to be the holiest of scripture. They eagerly devour any new novel and strive to emulate its dragon characters in all things.
The seventh head, whose name is Draco, can't stand Anne McCaffrey's work, which he considers a load of tripe. He eschews the telepathic communication affected by the other six heads and is usually to be found reading Shakespeare.
While their tastes in literature may not agree, there is one thing that unites all seven of the Dragon's heads. This is their is hatred for Cerberus, guard dog of the Greek underworld. What it is about Cerberus that offends the Dragon so much, we may never know, but he regularly swims the Rver Styx to make his displeasure felt.
Next: Angels and demons.