Squire Left was not always a Squire. At one time he was an apprentice black smith. One eve though, the village was attacked by Dun'no and Murtog. During the raid he lost his left arm when his hut caved it. Having lost his arm, he considered useless as a smithy, so he was cast out. He swore revenge upon the monsters. By some unnatural force, an old magician heard his oath, and granted him a magical arm that transforms into any tool he could dream of. He also granted him superb strength. He then went in search of a knight to take him as a squire. Mustach was the only one willing.
Yes, i'm going to paint this when i gets paint.
ok, i made a small change to the story. instead of a morphing arm, the magician made him an arm of living bronze, where the fore arm could be removed and replaced with another one, with a certain tool he might need.