From what I understand throughout the game so far, and I may be wrong. It is also what allows us to re live a battle over and over again until we find the outcome of the future that allows us to succeed. So also a lore friendly way as to why we can 'die' multiple times within a trial or dungeon, but still complete it as if it were only our first try.

For Zenos, being he also had the echo it was similar to constantly playing a game of chess, but every other move each made was a check mate and we were locked in a stale mate


As stated above it does more than just that. What I do not believe it does is makes us 'Hydaelyn's chosen', she just chose people who possessed the echo to be her 'chosen'.