Draco Malfoy
Draco will be irritable, snappish, feeling drained and tired more easily and will begin feeling rather paranoid as if someone's following or out to get him. He'll wake up from bad dreams and be otherwise fine at first, but throughout the day he'll be feeling a pain in his upper arm but there appears to be nothing wrong - until later when he checks his arm and notices really strange scarring.
As a way of trying to cope he'll be writing out in his book (not journal, the one he uses for writing) and it'll just flow out without really any thought at all. It's not until later when he reads it over that he starts worrying about what he's written.