Cooperation | Cooperation mode SC II: Legacy of the Void Guide

The presence of the second player on the map in theory changes the game, but in practice it doesn't have to. It all depends on how good the second player is, which character he controls and if you and him are able to get along. It might happen that you will have nothing to do because the second player will complete the whole mission on his own and he will destroy all enemy bases despite the fact that mission objectives don't tell him to do it. It might also happen that you will barely manage to complete the main objective because you and he will be not able to cooperate or you will be forced to act alone. It is especially important on maps where few mission objectives must be completed simultaneously. Due to that, you and the other player should make a plan at the start of the game. If the mission objectives are scattered across the map, share them. If the mission is about protecting an object, decide who will protect which base entrance. Decide where you will gather units for the attack and who will create anti-aircraft units. On the normal difficulty level you don't have to decide about everything, but on high and brutal the lack of communication will surely lead to a failure.

Despite appearances, you don't have to pick characters controlling two various races. Two terrans have similar chance to complete the mission as two zergs or protoss. The difference is mostly in preferences, as some characters are better in attack and others are better in defense. For example, Zagara is a great character for attacking enemy positions with a wave of weak units while Swann with his mining laser and turrets will be much more effective when defending the base.