Having recently overrun the Kingdom of Kashuan, Emperor Mateus of the Palamecian Empire decides to continue the expansion northwards. Considering the Dragoons too powerful to attack with conventional means, the Empire poisoned the water supply of Deist, killing nearly all Wyverns. The Empire then invades the island with its ground army, and the Dragoons, now without their partners, are no longer a match for the Emperor's troops. When the Palamecian Army attacks Castle Deist every remaining Wyvern but one is killed. Ricard Highwind is the only Dragoon that survives the Palamecian onslaught.
If the party visits Deist, Elina and her son Kain will tell them about the invasion and the near-extinction of the Wyverns.