When Billy arches Draco loses his ability to pull off sarcastic disinterest, if the way he muffles a quietly pleased growl into a harder bite is any indication. Any hint of amusement is overtaken in favor of swirling a twisting line of heat down Billy's chest toward his abs, and only a little lower.

He pauses there, smirks, and shifts off, finding his wand long enough to swirl that too and somewhat loosen the thread of magic holding Billy to the bedpost. The thread binding his wrists remains firmly tight, but he should have enough slack now to-

"If you wouldn't mind rolling over for me... "