Protecting her meant disappearing. He almost made that mistake.
Dorian Vex has always been the quiet one, the gentlest of the four, the one who makes Isla feel safe before he makes her feel anything else. When Chancellor Voss threatens his family's already modest standing in a private meeting no one else witnesses, Dorian doesn't tell a soul. He starts pulling away instead, convinced that protecting the people he loves means protecting them from himself.
The others read his withdrawal as distance. Only Isla senses it's something else. Alone in Earth House's old archives searching for anything that might shield his family, Dorian finds an early reference to the Veil's true origin instead, and has to decide whether staying, and telling her everything, is worth the risk he's spent his whole life avoiding.
No duel. No audience. Just a boy who finally chooses to stay instead of disappearing.