There hadn't always been such animosity, between the Earl and the Marquis. Quite the opposite, in fact.
The Marquis had been the Earl's trusted friend, once, before circumstances and his own error had forced him to move on.
That had been the Earl's big mistake. The Marquis de Carabas was only your friend for as long as you had something to offer him.
The Earl had been a handsome man in his youth, a fighter and a lover, before age and senility stole away everything he had once been. The Marquis had offered him a deal.
Help in the war on the Raven's Court, in exchange for sex at a time and place of his choosing. That was where he had miscalculated: he had chosen exactly the wrong time and place.
Because he was caught unprepared in the Marquis' bed, the Earl lost the battle for the White City, a dozen men, and his eye. He never forgave his former ally.
But in his more lucid moments, he still remembered things as they had once been.