The Lorekeeper's Tome

Vyrmordax the Caustic is a black dragon of terrible age, and one of the two guardians who have kept the world away from the Obsidian Crown for longer than living memory. He lairs on a far island in the southeast of the Reach, in what was once a proud fortress of an elder age and is now a corroded, dripping ruin his own acid has eaten down to a pitted shell over the long centuries. He is vast, patient, and venomous in every sense, and he does not guard the island's prize alone - he keeps his watch beside a master of dark arts, and the two together have made the island a death-trap that none have crossed and returned from. To reach the Crown, one must get past Vyrmordax, and the great black wyrm has had a very long time to grow bored, and bitter, and cruel.