Why shall those 4 cities be razed?

It's important to understand that the entity is a very astute and well versed thing in the arts of war. As such one of it's fall back plan is to revert to it's dream or ambition, as a form of decoy or cloak. Sadly this plan must be denied to them. And as a mark of surrender, in the eventually at least very modest of them freeing themselves, or as necessarly evoqued following the destruction of the entity, those 5 areas must be razed. A reminder.