Mimantean

Draughts from the fount of Nile [...] or the steep Mimantian height, Snow-capped

This is puzzling because Mimas is closer to Saturn than Enceladus, and the Mimantean orbit is much more eccentric (out of round) than the Enceladean orbit.

a global thermal event early in Mimantian history erased all record of ancient impacts

I went back to the grind of reviewing that day's Cassini photographs. Imagine my shock when I noticed that Mimas, one of the inner moons of Saturn, had acquired a concave depression in it since the last fly-by! Of course, I immediately realized that the Mimanteans had constructed a fully armed and operational Death Star!