What does "Resist:Magic (-200)" mean in a spell wiki page?

[loramin]

I believe it's saying you use magic resist to avoid that attack, but do so as if you MR was 200 less.

I should note that whenever the wiki references a number that players can't measure, you should take it with a grain of salt. The number probably comes from live data, and so it might not be the same number on our (classic-customized) server.