The dragon starts in its sleep, shocked into wakefulness. Ears which can hear grass grow have no trouble picking out the clinking of glasses and the raising of toasts in the village below its cave.
The ritual, it realizes. The oldest game. No one should even know about it, but somehow, someone does. They have gathered the thirteen, and dedicated to their purpose. Thirteen against one. The one is a dragon, and it should hardly seem fair, but the dragon worries still. Whoever brought them together must have known that. Must have chosen accordingly. The game would laugh at anything less, and all the thirteen would achieve would be their own humiliation, followed quickly by their deaths.
Resting its mighty head upon its forepaws, the dragon wonders at who it could be and what they could intend. Before it falls asleep once more, it wryly acknowledges that it will know soon enough.