Every five years or so, a true summer's warmth comes to Null. The endless ice recedes to mere memory, one's breath no longer clouds, and the rumors of brain worms return. Not every warm summer heralds a plague year, but there have been three in the last century and a half.

Often the only indicator that a plague year has begun is when the first victims die. Victims spend several weeks behaving erratically; behaviors may include sleeping excessively, randomly assaulting strangers, writing bad poetry, and hallucinations. Those who don't kill themselves experience seizures in the last hour before death. After death, arm-long maggots (the aptly named "brain worms") crawl from the corpse's eyes, ears, nostrils, and mouth. The worms die a few hours after their host.

Each time the worms have returned, they've dramatically changed the city of Null. They show no respect for rank or religious fervor, taking down lords and fishermen with equal ease. Political upheaval is expected during plague years. Those with the resources often flee the city, leaving many factions without competent leadership. The madness induced by the worms undoubtedly contributes to the destruction.

Twenty-six years ago, the Sarmunadi section of the city was burned to ash by a mob attempting to stop the so-called Ancrites from seeding Null's water supplies with the plague. Null lost a tenth of its population that summer.

The goods, temples and priesthood of Enchiari The Golden were looted, burned, and hung respectively seventy-nine years ago. This was apparently a mild outbreak; the estimates at the time claim roughly one in twenty-five caught the plague.

One hundred and forty-three years ago, complete anarchy erupted. Armed gangs of thugs, looters, and soldiers led by worm-maddened leaders stormed through the city. Food, water, and corpse removal became huge problems, preparing Null for a second plague. There aren't clear records to estimate the changes in population then, but I don't doubt that a summer of Brain Worms followed by the Swollen Death made Null a much smaller city.