As you progress further from the center of a Timeline, you will start to find echoes with the Shade of Orobyss within.

Defeating the Shade adds Corruption to the timeline, increasing its difficulty and rewards and certain items dropped by the Shade require a minimum amount of Corruption. It also brings the echo web for the timeline back to a fresh state, allowing you to start again with a higher potential for rewards.

Defeating the Shade does not reset your Timeline Stability or the active modifiers you have.

Corruption increases item rarity, experience gained, monster health, monster damage and how much Timeline Stability echoes give.

Corruption also increases area level in standard timelines, and increases the rarity of guaranteed echo rewards in Empowered timelines. Corruption also, very slightly, increases the odds of unique items having Legendary Potential or Weaver's Will.

Standard timelines start at 0 corruption and have a maximum of 50. Empowered timelines start at 100 corruption and have no maximum.

Defeating Shade in a Timeline that has much lower corruption compared the Timeline with the highest corruption, making it much faster to progress corruption when moving between Timelines. The amount of Bonus Corruption defeating a Shade will be shown on the Echo before entering it. Defeating Shade with Gaze of Orobyss grants additional Corruption.

If the Corruption on a timeline has been increased, it can be lowered by completing Sanctuary of Eterra Echo connected to the entry point.