When telling the story of the , the provides the only mention of these creatures: "The colossal Wyrms, of whom today's dragons are a pale reflection, turned all the sky to fire, while on the ground armies of foot soldiers, and and , filled the valleys and plains with blood".
A Mystic Knight demonstration of Perfect Blocking of several of the Wyrm's attacks (Ice breath, grab attack, High Exequy and High Bolide spells cannot be blocked). In this video the Arisen demonstrates 2 wing buffet attacks, 1 High Frigor, 2 forward charges, and 1 arm swipe. (Hard mode, without the augment)
White Wyrms can polymorph into human form and surprise the unwary traveller. Clicking the White Wyrm's paperdoll in his polymorphed shape will show you it is "a white wyrm the mystic llamaherder".