King Rust's murdered queen, whose death he half-confesses he should have answered differently.
Twice in the parlay King Rust reaches for his dead wife. Explaining why Princess Formidable cannot be talked down, he says that of all his children she is the most like her mother — both the most stubborn and the most superstitious. And after Carl mocks him for having all three children on the field, Rust refuses the bait and instead trails off into something else entirely: "That moment my wife was killed, I should have..."
He never finishes the sentence. Carl reads him as utterly defeated. The unspoken regret is the closest the chapter comes to explaining how the Skull Empire's royal family came apart badly enough to end a solar system.
Rust's murdered queen, source of Formidable's stubbornness and of his own unfinished regret.