"Same principle, different way of going about it. I spent a year researching a version that centers the effect on the casting magician. Screws up most forms of detection in a constantly shifting area centered on me instead of a target. I don’t think they’re going to have time to run a computing of average transients to figure out the algorithm for the shifting. Besides, it’s keyed to magnetic field fluctuations. I always knew that funny little deposit of magnetically sensitive ferric bone above my sinuses was good for something. They won’t work that one out. Nice big area, too. The barriers I’m erecting are a bit more limited in scale, but we shouldn’t have to worry about anything less than a cascade of automatics or a firework display of multiple grenade launchers."