Welcome to Harry Potter Theory. Today we’re going to be discussing Hogwarts Headmaster Albus Dumbledore, and trying to unravel one of his dirtiest darkest secrets.
As early as the Philosopher’s Stone (in the first chapter, no less), we hear Dumbledore mention a certain scar in a conversation with McGonagall. But it’s not the scar that you probably thought of, Harry’s scar of legend, it’s actually one of Dumbledore’s OWN scars. 
If the first place your mind went to was emotional scars then that would make perfect sense, as Dumbledore, who lived quite the tumultuous life, would be riddled with them. 
But in this instance we’re talking about a real bonafide scar. 
Let's dive in...