The Marquis de Carabas is not lusting after the Upworlder Richard Mayhew.
He was an Upworlder himself once, before slipping and finding a much better place to practice his art, and he knows what they're like.
For another thing, Richard and the Lady Door have been getting increasingly close since he returned to them, and the Marquis doesn't want to end up owing the girl the biggest favour of his life, for stealing her man.
But sometimes he wakes up gasping and sweating, from dreams of dark hair and a deft hand with a spear.
He blames Croup and Vandemar.