User blog comment:The Milkman/Indoctrination Theorists Say the Darndest Things/@comment-5306852-20121022203436/@comment-4237253-20121023210835

Well either way, the Crucible itself is a Deus Ex Machina device, on a larger scale. It is introduced early on in the final instalment of the series as a means of ending the Organic vs. Reaper conflict.