Barty Crouch Junior stood perfectly still, staring at his Lord's giant wand. Said Lord stared at him with impatience.
"I promised you you'll be able to play with it if you joined me, so what are you waiting for?"
Barty grins eagerly, and then he gets on all fours and begins to lick the wand with fervor. He could feel his ectasy growing as he does. Then his Lord pulls away.
"Every wand needs a holster," his Lord speaks. "I think your insides would do."
And then he feels pain as his Lord pushes the wand inside of him. The pain doesn't last long before it morphs into pleasure.
"Are you enjoying yourself?" his Lord asks, but Barty suspects he already knows the answer.
Even so, he is unable to say anything, so he just nods. This seems to satisfy his Lord.
"I was hoping you'll say that," he says
Then he switches their positions so that Barty is sitting on top, the wand still deep inside of him.
"Now ride," his Lord demands. "Ride while I watch."
Barty starts to do so, slowly at first, but then he starts riding faster and harder. By the time he is done, his Lord is reduced to a mess. Which is oddly satisfactory for some reason.
"I may be in charge in public," his Lord says when he is done. "But in private, you're in charge of me."