The MMO Griefer idea was running around in my head while I was out doing yard work today. It's hard to keep the mind from rambling when cutting up fallen trees and such.
Things like--what's the Griefer's reason for travelling? What value would the background add to a character in the game, what would they bring to a group? What skills would they have? Life events? And so on.
An obvious reason for Travelling would be that they're being stalked IRL by the members of a large number of guilds, clans, and other multiplayer assemblages of people whose line they've crossed. Gave up MMOs and took up travelling for their health, as it were.
As to skills, one could presume that the character developed some social engineering and computer skills. While this isn't necessary for griefing, you could presume that those who never develop these skills never get the chance to become travellers.
A downside might be something along these lines; if they ever access a networked computer system, for any purpose or in any way, they have something like a 1% chance per year as a griefer of being noticed on the network by someone who is actively seeking to settle a score with them.
What else belongs in the griefer background?