Disclaimer: I own neither Highlander nor Harry Potter.
A/N: Deeply inspired by Louis IX's "Voldemort's Last Spell"; you should definitely read it; It's my favorite story on this whole site. It pretty much embodied exactly what I was looking for, and he's a very skilled writer. I've decided to try my own hand at something similar – as the idea knocks about my head quite a bit – with probably a fair few crossovers written into the subplots, so try and stay with me.
When he was five, he was already weary of the world. He understood how an action - even a small, harmless action - would result in horrible consequence. He also understood how he would be punished, even when no action had preceded it; how sometimes, senseless pain was caused, without provocation of any sort.
When he was five, he learnt that the world wasn't a fair place. His cousin - dumber, fatter, and uglier - was treated like a prince, undeserving of his spoilt greed and gluttony. His cousin was never punished for pushing him over, but the reverse was simply sacrilegious. The world itself seemed uglier because of it.
When he was five, he learnt how to persevere and to work hard. Because if he didn't, then he wouldn't get to eat. Sometimes, they forgot to feed him anyway, even if he'd done all they'd asked for. He understood hunger - starvation - the kind that slowly gnaws away at your stomach, and then your mind, before you become half delirious from it. To the point where he no-longer felt hungry, but empty to a degree that he couldn't understand, and didn't know what to do to feel better again. Sometimes he wasn't sure if he wanted to, that maybe feeling nothing at all was better than the loneliness and pain.
When he was five, it was only in age that he embodied it. Not even his body showed it: malnourished but sturdy, from long hours of constant work. His face was gaunt and his eyes had dulled, dark in their sockets that looked at nothing but the next task at hand. His appearance caused his aunt to never look him in the eyes; to whisper 'freak', even when she knew he could hear her.
When he was five, his magic had had enough.
When he was five, Harry Potter disappeared.