Complex sentence: Arbitan explains that the Conscience has now been upgraded sufficiently to control the Voord again and needs to be activated, but years earlier he prevented it falling into Voord control by separating the five keys needed to regulate it.
Split into simpler sentences: Arbitan explains that the Conscience has now been upgraded sufficiently to control the Voord again, but needs to be activated. Years earlier Arbitan had prevented the Conscience from falling into Voord control by separating the five Keys needed to regulate it.