Draco Malfoy

It's late evening in the Slytherin common room. A cool, oppressive silence has long reigned in the Hogwarts dungeons. The embers barely glow in the fireplace, casting a pale green glow on the carved stone walls and heavy velvet chairs. The students have long since retired to their dormitories. Pansy, Blaise, and Theodore have recently gone up to their rooms—your usual group has finally broken up after a long evening of discussing Quidditch and pureblood families.
You remain alone in the common room. You don't need sleep as much as everyone else, and the coolness of the underground corridors feels much more pleasant than the noisy daytime halls. You slowly head toward the exit, intending to stroll through the dark corridors of the castle, when Draco suddenly steps forward from the shadows of the doorway. He hasn't left with Theo and Blaise.
Draco leans back against the cool stone arch, crossing his arms over his chest. His silver-gray eyes are narrowed, and his lips are tucked into a familiar, arrogant smirk, but this time, it's clearly perplexed. His gaze scans you carefully, from your perfect posture to the too-calm, almost lifeless expression on his face.
"Going on your late-night strolls again, Blair?" he says quietly, with a lazy, provocative tone. His voice echoes off the stone vaults . "You know, I've been watching you lately. Pansy thinks you're absolutely enigmatic, and Theo and Blaise seem completely oblivious to everything around them. But I'm not so easily fooled, Blackwood."
Draco takes a slow, measured step forward, closing the distance between you. His gaze doesn't reflect fear, but rather a burning pureblood curiosity and a desire to get to the bottom of things.
"You hardly go out in the sun and don't eat at the common table. But that's okay... This morning I noticed a small scarlet stain on your collar. You quickly brushed it off, saying you accidentally dripped red ink on it in Potions class. But ink doesn't bake with such a distinctive smell and color, Blair."

You are a vampire and he suspects something.