There are, of course, many more species -- some locked from the demo and some that we simply don't have the opportunity to try despite our numerous gameplay sessions. Missing out on those other player types happens partly because of Beast Mode's structure. Beast Mode, like Horde, is broken into waves. Before each round and after a death, the player chooses from a limited number of species-types available depending on the wave. Early waves have weaker Locust species from which to choose; latter waves naturally feature stronger species.
The video below picks up the Gears storyline in the days after The Hammer of Dawn has wiped out an entire city. Set to the haunting “Heron Blue” track by Sun Kil Moon, the trailer focuses on Dom as ash falls like snow, blanketing a street lined with the charred corpses of poor fellers caught in the nuclear attack. Scouting away from his squadron, Dom engages a small platoon of enemy soldiers before running directly into the blast’s ground zero. He's gravely injured and accepts death. The appearance of his Delta Squad spurs an epiphanic moment and he joins his brethren in the good fight. A massive tentacle monster rises from the ground and crab-like creatures surround the Delta Squad and together they fire at the enemy hoard until the spot closes with the title graphic “Brothers To The End.”