Sir Scarecrow is a character you meet during the tutorial.
For the boss version, visit
You meet Sir Scarecrow in the beginning in the game. He's the person that teaches you how to play the game.
He shows up at a certain point in the game, when you have to kill a bunch of scarecrows, he says something about killing his brethren, and you only see him once again.
You also see him during the trainings (except for the archery one)
The final message you get from Sir Scarecrow during the tutorial.