Once you unlock "wand" then here are the keys to use spells. They have cooldown times so it will take a second or two to use another spell. Here are the keys: A = Avada Kedavra S = Silencio D = Densaugeo F = Flintifors G = Glacius H = Herbifors J = Jelly Legs curse (incantation locomotor wibbly) K = Knee Reversal Hex (Spell is nonverbal, incantation unknown) L = Lumos Space Key = Levicorpus
Well, someone tested it out so thanks to them! Won't reveal their name though!
