we knew only that ambergris played host to some of the world 's greatest artists ; that it was home to the mysterious gray caps ; that a merchant clan , hoegbotton and sons , had wrested control of the city from a long line of kings ; that the kalif and his great western empire had thrice tried to invade ambergris ; that , once upon a time , some centuries ago , a catastrophe called the silence had taken place there ; and that the annual festival of the freshwater squid often erupted into violence , an edgy lawlessness that some said was connected to the gray caps .