Back to Hogwarts
A year ago, at the Addams' mansion, he'd learned a very useful skill. Speaking his words, for small things like locking doors, made the magic stronger. More focused, and more powered. H'ed learned to use this to lock his belongings, focusing on the object, door, or case in question and whispering "Lock". He'd prevented countless pranks with the simple spell that he'd taken to call a charm. Simply concentrating and whispering what he wanted an object to do. And it wasn't a hard task. He was just encouraging the objects to do what they wanted to do. A lock wanted to lock, so it would lock. A ball wanted to roll, so it would roll. And a plant wanted to grow. So it grew.
As he walked down the hallway, following Professor Snape, he looked at the straps of his bag. "Close. Lock. Seal," he whispered, zipping close any loose ends and sealing them with magic. His bag glowed a faint green as it followed his commands. Noting the fact that the torches were getting dimmer the more they went down, Harry summoned a ball of green light, squinting as his eyes re-adjusted to the darkness of the hallway. He jumped slightly as the professor spoke. "While I must admit your display of magic is admirable," he started, turning the corner. "The color of that light will make me lose my mind," it took him a moment to realize what he was inferring. He willed his ball of light to turn into a softer yellow, barking out a habitual "Yes, Sir," that came out of a year of calling just about every adult he knew sir or ma'am.
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Snape paused slightly at the boy's words, before continuing on. The short, purposeful "Yes, Sir," made the boy sound more like a muggle soldier, a sharp change from the long, bored and often rude answers he received from the Gryffindors and even the smart-asses from his own house. He wasn't sure how he should feel about it, cross referencing it with the muggle comic series The Avengers and the character Bucky Barnes.