Somehow forces of the Adeptus Mechanicus managed to meet a patrol of Plague Marines of the Death Guard on a heavily forested jungle planet and they fought it out in the hot and humid conditions for mastery of the battle grid.
The Ad Mech played for the objectives more effectively than the Plague Marines who, ill-advisedly, concentrated on killing as much as they could. The Ad Mech's strategy was the successful one in the end.
These are two of the weirdest factions in the game and provide an interesting array of different troop types, weapons and strategies. Moreover, they are great fun to paint.