"The Locust never died, James."
—Former Sgt. Marcus Fenix, after being freed from the Swarm network.

The Battle of Osmium Mine Bravo was a small scale encounter that took place at the start of the Swarm War in an old COG osmium mine located beneath Fort Reval. During the battle, a small group of Outsiders led by former lieutenant James Dominic Fenix succesfully rescued James' father and the squad's leader, former sergeant Marcus Fenix. The battle was a part of the mission to Fort Reval, aimed at investigating the mine's Locust burial site and its possible connection to the Swarm.

Order of BattleEdit

Entering the MineEdit


Del, JD and Kait look down at the entrance to the hive.

After getting off the destroyed ore transporter at 01:19, JD, Del and Kait head deeper into the mine. Kait seems surprised that the mine still has power after all these years and Del explains that old COG mines are powered with geothermal energy. In the tunnels, they stumble upon a dump of old Locust weapons like the Hammerburst II assault rifles and the Boltok revolvers, a dead Outsider surrounded by Juvie corpses and a "TURN AWAY" sign written on the floor with blood. The team enters a huge cavity and sees a tunnel leading into the main part of the hive. Going down the staircase, JD finds a Locust shell. Del mentions that the Locust crystals are so hard they can shatter diamonds. Moments later they find a cluster of shells. As Kait tries to inspect one of them, a large humanoid resembling a Locust Drone emerges from the behind of the shell cluster and attacks the team with another similarly looking humanoid and a group of swarm drones strengthened by a strange gas generated by their larger comrades. After dealing with the group, JD, Del and Kait are shocked to discover that the Imulsion Countermeasure Weapon did not kill the Locust, but unbeknownst to the entire human population of Sera, forced their bodies to form crystal cocoons and evolve over the last 25 years, meaning that humanity - once again - finds itself at war with its sworn enemy.

Finding MarcusEdit


Marcus moments after being pulled out of the pod.

JD and his teammates find a mechanical loader and use it to break through Swarm-controlled tunnels and finally reach the center of the hive, where they battle the snatcher that kidnapped Marcus. Knowing time is of the essence, JD, Del and Kait search the hive for a fresh-looking pod. They manage to find one and cut Marcus out of it, though he appears to be dead at first. JD desperately tries to make his father breathe and breaks down while Del tries to comfort his friend, telling JD he should let Marcus go. The young Fenix cannot accept the possibility of his father dying and after a few seconds, Marcus starts to expectorate the liquid from the pod. He grabs JD's hand, as he tries to help him. Marcus wakes up and coughs from rest of the liquid stuck in his respiratory tract, then JD calms him down and assures his father he is safe. Marcus tells JD and the rest of the group that the entire hive is a connected network that he accessed while being podded, which allowed him to feel all the abducted people and learn that the Locust evolved into "Scions" - The next stage of their evolution and are now using the kidnapped people to grow an army for the coming war. He also informs Kait that all people from Fort Umson - except her mother, who is being treated differently by the Swarm - are dead. While saddened, Del mentions Oscar, JD tells Kait he is sorry, but she quickly responds that mourning their friends is not going to help her mother. Marcus adds that Reyna was taken to another burial site at the Tollen Dam, not far from their current position. With Marcus rescued, the entire group prepares to leave the mine.

Getting OutEdit


The team escapes the mine.

Despite numerous Swarm reinforcements trying to stop them, JD, Kait, Del and Marcus make their way back to the mining shaft and with the transporter destroyed, Marcus and Kait hold the Swarm off, while JD and Del are trying to figure out a way of getting back to the surface. JD tells each of the rest to grab one of the wire ropes and shoot the bolts connecting them to the transporter, which causes the counterweight to eject them up just in time before the Swarm can overwhelm them. While traveling back to the surface, the entire shaft starts collapsing and the squad almost gets crushed by the gears of the lifting mechanism. JD, his father and friends climb up the ropes, exiting the mine and proceed to the nearby Tollen Dam and its burial site.[1]


The expedition to Fort Reval, despite its difficulties, turned out to be a success. The team led by Marcus and - in his absence - JD managed to gather crucial intel on the disappearances and the creatures responsible for them, including the discovery of the Locust evolution into Scions, the true reason behind the Locust crystallization.

The success of the expedition can be partially attributed to the Swarm itself, as podding Marcus gave him access to important information, like the location of Reyna Diaz, the existence of the Swarm hive mind and a confirmation regarding the return of the Locust Horde - Information that would not be obtainable in any other way.

While the Locust evolution seems at least partially explained by the discovery, the origins of the Swarm biomass, network, evolution cycle, Snatchers, Pouncers etc. remain a mystery.

Contradictory to Marcus' information, Oscar Diaz survived the attack, but was later killed during the Siege of Riftworm Village.


  1. Gears of War 4: Act III: Origins/Act IV: Get Out

Battles of the Swarm War
42 A.E. Rescue of Fort Umson (Ambush on Fort Umson · Mission to Fort Reval · Battle of Osmium Mine Bravo · Mission to the Tollen Dam · Skirmish in Speyer · Assault on the Tollen Dam) · Skirmish in the Wilds · Ambush on South Village · Mission to Fort Umson · Mission to Orzabal Crater · Mission to South Village · Mission to Azura Research Facility · Evacuation of Settlement 2 · Ambush on Croya · Ambush on Bravelle · Ambush on Holdstead Croft · Ambush on Five Pines · Ambush on Pasco's Village · Mission to the Great Seran Rend · Skirmish on the Jacinto Plateau · Siege of Riftworm Village · Second Mission to New Hope Research Facility · Incursions in Kadar Valley · Mission to Mount Kadar Laboratory · Mission to OZP-11 · Battle of Old Ephyra · Hivebuster Offensive (Hivebust of Pahanu Island · Mission to Croya · Hivebust of Bravelle)
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