Y/n pov:

I sit in my common room in the training room as I feel my metal arm shift and mold itself into a new shape. When it finishes it looks like a cannon with a curved extendable blade on one side.

I look at it amazed before aiming at a training dummy and it fires a blue ball of plasma that obliterates the dummy and I notice that I barely felt the strength of the kickback from the shot as it molds back into my hand.