| Spoiler warning! This article contains plot details from the latest book. |
Echoes are remnants of shadowflux. Lady Zillah mentions them in the seventh book, Flashback. When Sophie and Fitz have echoes, they cause them immense pain. Fitz has one on his heart, so he feels pain whenever he gets emotional. Sophie has one in her head, and one in her hand. She feels pain when her anger and fear take over, causing a "monster", metaphorically speaking, that makes it harder to calm her echoes. Everyone's echoes are different. They can take different amounts of time to go away for each person. The triggers can also differ.