A specific kind of crystal, known as a vibration crystal, found its application within an arc array. Before the period known as the Bandit purges, Captain-Inspector Magna Tolvan journeyed to Accresker Jail to have a discussion with Chelli Lona Aphra; during this encounter, Tolvan requested that Aphra enumerate the elements of an arc array as a means of concealing their exchange from a nearby Imperial interrogator.