A really good way to get this achievement relatively quickly is to play on easiest mode against the Magyars on a tiny map. The Magyars will not build a castle in the initial moments, but will try to make stables and siege instead. So what I did was I have one villager build houses, two build a barracks or stables (depending on your civ) and send the scout to harass his villagers and keep them in the town center as much as possible until your troops begin to trickle into his base. After you have a few troops trickling into his base, just keep sending your villagers forward making barracks and stables and castles on his doorstep and you should overwhelm him quickly. I'd win a game in about 6-8 minutes. Bonus is you get a win for whatever race you are playing as also.