…to a province, to be governed by a viceroy from hence, and to destroy and put to death, not only all the Big-endian exiles, but likewise all the people of that empire who would not immediately forsake the Big-endian heresy, he, the said Flestrin, like a false traitor against his most auspicious, serene, imperial majesty, did petition to be excused from the said service, upon pretence of unwillingness to force the consciences, or destroy the liberties and lives of an innocent people.
There are no more uses of "serene" in the book.
Show samples from other sources
While I lie awake worrying, she sleeps serenely.
She remained serene even when he was yelling at her.