Walkthroughs for custom maps.

I need help with the "Strength and Wit" campaign. I'm stuck on the second mission, where I have to defeat the Knight of Horror with snipers. I've already found everything on this map, collected the anti-magic spell, the slow spell, and all the artifacts (2 on the field + 2 from the peasants), but I can't figure out how to defeat the knights. If I use anti-magic on the snipers to prevent them from killing me with their explosion, I don't have time to slow them down, and they come out. If I slow them down, the explosion still kills me. Please advise on what I should do.