Chess is in the third set of Special Ops maps you unlock. You unlock it by finishing all five of the Frigg missions in conquest. The map is shaped like a chess board where one color square is represented by a higher elevation and the creeper comes from the opposite side of the map from you.
Strategy: http://www.youtube.com/watch?v=1UNju3cEVDs&feature=youtube_gdata (a link to the video walkthrough or the video here would be awesome)
Strategy Step by Step: