In the end, there was little the Cel could do to resist, so it didn't.

Far off, in the deep and particularly dark stretch of space, the Cel savoured the knowledge of new civilizations to subjugate and subsequently exterminate. Well, some of them did. The frigates to escape the conflict of First Contact were captured and hastily brought under the control of a particularly powerful vassal of the Emperor who deemed this information too valuable for his fellow lords. The wealth of knowledge that could be assimilated could boost his power in the empire a million times over.