CW is set to release an epic four-episode DC crossover come Monday. Marking the first time mashup of Arrow, Flash, Supergirl, and the Legends of Tomorrow, the trailer shows the gang fighting off an alien invasion. Getting a look at new footage of the Dominators, the aliens are set on taking over the Earth with their invasion ships. Who will win in this epic battle? The four-part crossover begins this Monday, November 28.