The abyssal trench is a very deep marine trench in the oceans of Sera.
During the Locust War, the islands on the far side of the abyssal trench from the Seran mainland such as Galangi, Pahanu, Weilhei and Vectes were protected from attacks by the Locust Horde as they were unable to dig under the trench in order to reach the islands. For this reason, Chairman Richard Prescott commissioned the construction of the Sanctum doomsday bunker on Pahanu in secret to guarantee the prolonged, generational safety of Tyran citizens holding strategic importance in the event that return to the Tyran mainland proves to not be possible in a reasonable timeframe. Sanctum was effectively meant to be "the failsafe to the failsafe" in case Azura ever fell and it had facilities to not just survive but to thrive, to raise, train, feed, arm, and coordinate entire generations of Gears. However, the volcano that provided the thermal energy that powered the facility proved to be too unstable for long-term sustainability and it had to be abandoned.
Although Galangi in the South Islands was protected from the Locust by the trench, the nearby island of Noroa was not. Bernadette Mataki helped to defend the island for eight years, but her group eventually decided to abandon it. Although Hugo Muir argued for potentially joining a Stranded group as he felt that Bernie's choice of Galangi was too close to Noroa, Bernie pointed out that not only did Galangi have infrastructure and people, but the Locust couldn't reach it due to the trench.
In 15 A.E., the COG were eventually forced to sink Jacinto City in order to stop the Locust Horde and relocated to Port Farrall. However, the survivors faced harsh conditions and repeated attacks by Locust survivors. In order to find a safer place, the COG began looking at islands as evacuation spots, particularly Erevall and Vectes as they were both on the far side of the trench and thus the Locust couldn't reach them. Due to Vectes having infrastructure, it was chosen. The COG subsequently abandoned the mainland completely in favor of Vectes. After this, the Locust War effectively ended for the survivors of Jacinto for the time being as the Locust could no longer reach them to threaten them.
Although the abyssal trench was able to protect the people of the islands from the Locust, it could not protect them from the threat of the Lambent Pandemic. The Lambent began emerging on Vectes in greater and greater numbers, eventually forcing the COG to abandon the island and disband. Weilehi also came under attack by the Lambent, but were able to survive until the Lambent were wiped out by the Imulsion Countermeasure Weapon.
In 42 A.E., the Swarm from the Hive on Pahanu were able to reach Weilehi and wipe out the Weilehan despite the abyssal trench preventing the Swarm from digging between the islands. This greatly confused Doctor Hana Cole as not even the Locust were able to do this, but Hana and Team Scorpio were able to discover that the Swarm circumvented the barrier that the trench had provided them by using lava tubes connecting the islands.
- Jacinto's Remnant (First mentioned)
- Anvil Gate (Mentioned only)
- Coalition's End (Mentioned only)
- Gears: Hivebusters (Mentioned only)
Behind the Scenes
- It's unclear if the abyssal trench near the Lesser Islands Chain is the same one as the trench near the South Islands. However, both locations are referred to as simply "the abyssal trench," suggesting that they are in fact one and the same.