Dresden's defense varies. Without soulfire, his shield tanks some potent stuff (IIRC it tanks a gigantic explosion of C4 at one point? As-in, enough to destroy a whole tunnel system). WITH Soulfile, it's considerably above that.
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Sburbopolis, Homestuck RPG: http://www.gamefaqs.com/boards/8-gamefaqs-contests/60981373