Core Q&A Expanded Answer
Time-Threads are possible paths through time that can be examined to judge the consequences of a proposed change to Breanna's timeline. Badb Catha, a Master of Tuatha Time Magic, teaches Breanna and her personal Seeress, Livie, how to work with them. Badb also etches a new sigil into Livie's staff, transforming it into the Tuatha relic Síol-Radharc, or Sight-Seed. With it, Livie can use her intent to find the Time-Threads relevant to a specific person, event, or proposed action, rapidly discarding possibilities that do not matter and identifying those that could affect Breanna's timeline.