Dude, Skarm killing Maggy? No offense but that's not going to happen. Most Maggies run something like 200+ Speed EVs as well as Timid nature and for Skarm to serve its primary function (Walling) it can't afford that much Speed, or enough Attack EVs for that matter. Just give your Skarm Substitute instead, that way you can phaze out maggy and retreat your Skarm. Killing Maggy is what Dugtrio and HP [Fire] Maggy are for, you silly person. :3