From publisher blurb:
Legendary items are those that are picked up by the untested adventurers who eventually become heroes of the ages. Unlike traditional magical items, legendary items grow with the wielder, becoming more advanced as new abilities are unlocked over time.
Within this short book you will find the history of the Crown of Chaos, the requirements to attune a character to it, and the abilities of it. In addition, the rules of legendary items are detailed.