Remnants are feelings of loss or pain. People who experience Remnants usually know that something is missing in their lives, but they cannot grasp exactly what is missing.
Remnants are created when something that should be isn't. The Great Breaks have messed with history, eliminating some things, like parents, and causing others, like the natural disasters that are ripping apart the Earth. Sera and Riq both experience Remnants. Sera's are about her parents and how she should know them, while Riq's are just pain, like he shouldn't belong there. Ironically, in "The Trap Door", he tampers with his family tree, therefore ensuring that he doesn't exist in the future. In "the Iron Empire", he refuses to go back with Sera and Dak. He becomes Hepheastion, Alexander's best friend.