From the book's overview:
Echoes of Chaos is a collaborative storytelling game about a group of time-travelling Tourists who set out on a disastrous expedition into the past and accidentally alter the future. In the game, the game master (GM) and the players work together to determine what happens, using dice rolls to determine how successful or unsuccessful various actions are. The GM does not roll dice in this game. Please note-Echoes of Chaos is a narrative-first game, the goal of these rules is to help guide the story more so than dictate it.
Echoes of Chaos tells the story of the greedy, dangerous, and potentially disastrous actions of the Tourists as they travel back in time to achieve a secret, personal objective. This can be everything from hunting a Tyrannosaurus Rex, to stealing a famous artifact at the time of its creation, to
attempting to become part of history by replacing (or killing) a major figure. Every major dramatic action creates an echo that will have drastic consequences on the future, but the Tourists don't care... at least, not yet. This
is the story of how these hapless Tourists loot the past and destroy the future: they may achieve their goal, but it will cost them dearly.