Long ago in the hot lands to the north there lived a Dragon named Daegis the Bold. He claimed that being bold was easy, as Dragons were the mightiest of all creatures and nothing could harm him.
His cousin Iuesus, a Wyvern, heard his claim and was offended that Daegis would place Dragons so far above Wyverns. Knowing that his cousin could not refuse a challenge of his daring Iuesus told Daegis that no matter how bold he was, no creature alive could drink the molten blood of the planet.
Scoffing at Iuesus’ claim Daegis at once flew to find a lava vent.
Plunging his face toward the heat he took a gulp of the boiling rock. The lava seared his throat and Daegis roared his pain, spewing forth flames as the lava burnt in his throat.
Seeing this marvellous response Iuesus, who had followed in the hopes of seeing his cousin perish, also flew down to the lava pool and eagerly swallowed a mouthful. But the fire burnt too hot for Iuesus and in horror he flew down to the sea to drown his pain. Upon gulping seawater he sighed his relief and a toxic steam issued from his jaws.
And thus to this day Dragons breathe fire and Wyverns breathe toxic steam.