"Yyyyyes. Sort of. Not in those words. Don't start off with that, say that you're a new sorceress that just started nearby, and you're planning to make a castle and start working in the area. Or if you've already done that, tell then that you've made a castle already, but you get more invisible points if you tell them before you make the castle. Be polite, but don't be meek, they're sorcerers and sorceresses, they'll think it means you're weak. Usually they'll take the hint about claiming a turf."