Defeat your opponent only using Marauders... because you don't have anything else. :) You mine with Marauders, you figth with Marauders, you do everything with marauders. The only other thing you can have is an automated refinery, but even that looks like a Marauder (you need gas only for upgrades). The map is Metalopolis, with destructible debris on the ramps to the high yield minerals, and I removed all vespene geyser except the ones at the high yield.
The map is currently only available on the EU servers. Have Fun :)
You should find it among the other melee maps.