So they are not a evil invading force like the zerg, or a ancient alien race like the protoss, they are evolution itself, sped up, connected by a dna-data transfering hivemind, without the dead ends.
And thats what they see in the CentrAIl, a dead end, its not a civilisation they attack, not even a intelligent machine (should such a thing exist) - its just difficult territory to live in, but comes time, comes rapid change why shouldnt they dwell on thos streets, and in those skyscrapers? They will one day graze upon the surface firefog of the sun, why should they be afraid of this dead end?
So why dont you come with them, travell along the roads of life, avoid the tiresome work you are bound to, the discipline of your society, the slow progress and complete absence of adventure. Why not journey with the journeyman?
Little space left to capture that feeling, just two trees.