As the monk grabbed the collar of Serraphs cape, Serraph reacted by crouching down, and in the same motion, drawing and slicing upwards with his sword, slashing at the monks wrist, which would effectively sever the tendons in his hand and a main artery as well.
It was not necessarily Serraphs desire to hurt the monk, but simply a move of self defense which had become natural to Serraph.
Throwing the cape off (but still in the cloak and on his jointed stilts) he went into a full run towards the forest. As he ran, he knew that anything might trip him and he was fully prepared to fall in such a way that would land him back on his feat unharmed.
He was making his path almost parallel to the elf. He was still in charge of getting her to Pelan. It would not do for her to die.