Character background

I took advice from my lecturer and have thought of a simple background story to apply to my character:

He is a fairly old wizard, one capable of great spells and power, but who's age shows in his movement; his walks are hobbled and his posture is poor. Although he is old and looks frail, he can run and keep up with the rest of the character's, but his runs looks poorly balanced and as if he needs to put a lot of effort to ignore the pains from his aching body.

As an example of this, I was looking at the cinematic trailer for the first World of Warcraft game, and specifically when you see the undead character enter the scene as you can watch below at 1 minute and 50 seconds in:

(here is the link for the video starting at exact time if you don't want to fast forward: http://youtu.be/dYK_Gqyf48Y?t=1m51s)