Disclaimer: I do not own the Hogwarts world, Blaise Zabini, Draco Malfoy, or any other character mentioned herein. I am not receiving any pecuniary benefits from this work.
St. Blaise was patron saint of throats, and so Blaise feels noticing them to be his duty. Granger's throat can barely be seen behind her wild hood of hair, but the winter-gold flickers of it interest him very much. Granger is nothing to him but an irritant, but he thinks snaring her would be entertaining. Potter's golden-boy throat and Blaise wants, idly, to make it match Gryffindor colors using Potter's red blood.
Draco's throat is best. Pale pale moonlight skin, ice glowing in the moonlight and framed by shimmering platinum hair. Blaise wants to bite the strong tendons he can see when Draco laughs, wants him to throw his noble head back in invitation. Draco's collarbone, with that hollow that shadows gather in. Blaise wants to pin Draco to the wall and lick all the shadows away and feel Draco moan deep in his slim chest. The clean line of Draco's jaw and the curve of his cheekbone shining wet with the mark of Blaise's tongue, and a necklace of bruises on Draco's throat.
Blaise tears his eyes from Draco and back to his essay on how religion affected magical history. He hears Pansy's controlled voice murmuring to Draco and the soft well-bred drawl of a response. Draco's voice is almost tender, a vocal form of the quiet smile that is not for effect and that no one is supposed to see. Blaise saw it once, when he woke in the night and saw Draco reading. (If Blaise ever looked into the Mirror of Erised, he would see Draco wearing that smile but with blood on his lips, would see Draco's eyes clear and light-filled and endless as Blaise imagines they must be when Draco comes.)
Pansy would know what Draco looks like when he comes, and Blaise envies her the knowledge. But he has seen Pansy weep in Draco's bed when she thought no one could hear, and he knows that no curse he could cast would hurt her so much as loving Draco Malfoy does.