Colloquialisms: Muggles, Mudblood, Merlin’s beard, Galloping gargoyles, Hold your hippogriffs
Metaphor:
“Well, first the committee took turns in talking about ‘why we were there’. Then I stood up and said my bit, how Buckbeak was a good hippogriff, always cleaned his feathers. And then Lucius Malfoy got up…”
Onomatopoeia:
"SMASH! The door was hit with such force that it swung clean off its hinges and with a deafening crash landed flat on the floor." (p.46)
Hyperbole:
"mountains of roast and boiled potatoes" (p.203)
Harry Potter and the Sorcerer's Stone