At least at the level I play at, knights are invaluable because of their ability to jump over walls and threaten multiple pieces at the same time - they're the

At least at the level I play at, knights are invaluable because of their ability to jump over walls and threaten multiple pieces at the same time - they're the piece most likely to create a successful fork (threatening two pieces of value at the same time, likely forcing your opponent to pick which thing they're more willing to lose)