I like the stuff the Ancestor says during the walk-up in that mission:
!In all my terrible researches, what I sought was a glimpse behind the veil, some crumb of cosmic truth. I found it here. And in that moment of brain-blasting realization, I ceased to be a man and became a thing, an avatar of the crawling chaos.!
!we are chained here, you and I, at the end of the world. Free yourself, rouse the Thing, and embrace the ineffable cosmic hideousness that lives within us all!!
And the victory quote, too:
!Victory... a hollow, and ridiculous notion. We are born of this Thing, made from it, and we will be returned to it, in time. The great family of Man, crawling, squirming, living, dying... until the stars align in their inexorable formation, and what sleeps is roused once more. To hatch from this fragile shell of earth and rock, and bring about our inescapable end.!
!So seek solace in a manner befitting your lineage, and take up your nugatory vigil, forever haunted by that sickening prose, echoing through the infinite blackness of space and time... ruin has come to our family.!