How does Livie use Time-Threads to guide the Warriors of Destiny?

Livie uses Time-Threads to examine the likely temporal consequences of a contemplated action. When Izzy proposes executing the Santones and Pictones chiefs for Celtic treason, she asks Livie to spin the Time-Threads. Livie determines that removing the chiefs will not negatively affect Breanna's timeline and might improve it. Eoin and Izzy can then concentrate on the strategy and timing of their assassination.