This page in a nutshell: A WikiMaster is basically the complete opposite of a WikiDoctor. He/she is selfish, possibly insane and is horrible.
A WikiMaster is a very mean, nasty Wikipedian. WikiMasters tend to bite newcomers, or block them for simple, newbie-typical mistakes. They also block people who try to get in their way of process. They do own a WikiTARDIS for a while, then they actually, literally own/pwn the WikiTARDIS and then lose it. Soon after, they will get blocked, probably by a WikiDalek, and end up getting a sockpuppet account, and hiding themselves, before again realising they truly are a WikiMaster. They then nick a WikiDoctor's WikiTARDIS and become the centre of attention. Soon they are exposed to be malicious, block MORE users, and end up getting blocked, before getting lost and going on Uncyclopedia.
Normally a WikiMaster can be a really uptight user who cannot resist blocking every user within their vision. Also, they don't exactly bite, no, they tear a newcomer limb from limb, throw him/her on the barbecue, marinate them, cover them in garlic sauce and then bite the remains, giving the rest to Grendel to chew on while he's not eating Geats.