Each zone you encounter in a Timeline is called an Echo.

An Echo has a layout based on its name and a randomly chosen modifier that it will add to enemies. The enemy modifier also affects the rarity of items you will find and how much experience you will earn.

As you conquer more Echoes in a row, the modifiers you select will start to persist for multiple Echoes. This means you will have multiple modifiers active at the same time.

Conquering each Echo grants Timeline Stability, which is required for unlocking Quest Echoes.

Echoes have a guaranteed reward for completing them. However, if you die before completing an Echo you won't be able to collect it.