Disclaimer: Draco Malfoy and Blaise Zabini belong to J. K. Rowling. I am not her. If I were her, Draco's character and the role of Slytherin House would be explored much more fully than they are.
Blaise sits in the shadows, and watches. Draco stands in the light, and burns, and Blaise would swear that the fire shrinks when Draco looks at it. It is almost as though the fire would not waste its energy trying to compete with a dragon. In Slytherin House, even the fire is too cunning to fight a losing battle.
In the firelight Draco's mouth looks crimson, soaked in blood, and Blaise remembers the first time Draco changed him. Third year, in January, Draco had gotten a small basket of ripe peaches. They are wizards, after all, and what's magic for if not to circumvent those pesky seasons? Draco had grinned delightedly, flashing sharp teeth, and had sunk near-fangs into the swell of one particularly delicious peach. And Blaise had looked at the peaches, then looked at Draco licking the scarlet juice from the curve of his left wrist, mouth slick and reddened, and wanted. Peaches have never been Blaise's favorite fruit, but it seemed like he could develop a taste for them after all. So Blaise had calmly asked if he could have a peach, and Draco had looked at him. Grey eyes wide in slight surprise, pale skin at wrist and mouth still damp with juice and saliva, lips slightly parted and red as Gryffindor blood, and Blaise would break his wand to know what peaches tasted like when taken from Draco Malfoy's sneering mouth. Then Draco had shrugged, and tossed him a random peach. Blaise nodded perfunctory thanks and bit into it. Soft and sweet, yielding to teeth and tongue, and Blaise absently wished that Draco had tossed him the peach with his left hand.
"Zabini." Blaise would rise from the dead if that voice spoke his name, and he opens half-lidded eyes to see Draco in front of him holding out a peach, slim hips and slender arm and aristocratic wrist curved into a harmonious whole. Blaise wants to break Draco into a thousand sharp-edged pieces and feel himself bleed, and now he understands how a serpent could have tempted Eve.
"Want a bite?", and Draco's eyes are glittering promises neither of them really understand, promises that sound like moans and taste like sweaty skin and feel like forever. Blaise reaches out with one long-fingered hand, and takes a large bite, eyes fixed on Draco's the entire time. Draco smiles, but on his prettily cruel mouth everything has the faint flavor of a sneer, and takes a bite from the same place Blaise did, and walks away. Blaise has, naturally, never seen a basilisk's gaze, but he imagines that a basilisk has slanted eyes grey as the in-between-places and a silvery sheen on his scales.
He catches sight of Pansy in the mirror on the mantel, and her eyes are fixed on him. Pansy is the one reason he might feel guilty possessing Draco. He knows that she loves Draco, and has for years, and Pansy is a Slytherin. Now she knows that he wants the boy she loves, and he might actually have a chance. Draco values Pansy, and she has influence over him, but Draco values Blaise too.