- This article is for the Jacinto Plateau region. For the city, see Jacinto City, for the multiplayer map, see Jacinto (map).
The Jacinto Plateau was a large granite plateau located in the COG nation of Tyrus. The plateau was semi-resistant to Locust Horde digging, and as such was one of the few remaining places of human civilization during the Locust War. Cities such as Ephyra, Jacinto City, Tollen, Ilima and Montevado were built upon the plateau, and after the passing of the Fortification Act, these cities were transformed into military fortresses, while the remaining sections of Sera were destroyed to prevent them from being used by the Locust. Several portions of the plateau were sunk in 14 A.E., and the plateau was finally evacuated during the final moments of Operation: Hollow Storm. The COG returned to the Jacinto Plateau in 17 A.E. following the end of the Locust War and Lambent Pandemic. They began to rebuild by recycling materials from the ruined cities. Ephyra was rebuilt as New Ephyra and other cities were used to build COG Settlements on the Jacinto Plateau.
- "Jacinto's the one place they can't dig through..."
- —Sgt. Marcus Fenix to Pvt. Benjamine Carmine.
Jacinto Plateau was one of the only places in Sera where the Locust Horde could not penetrate the ground with Corpsers and digging machines, though natural fissures and utility systems riddled the rock. When the Locust tried their hardest to break through the granite substrata of Jacinto Plateau and eventually achieved success, the COG flooded these openings with nerve gas or sealed them. The surviving military leaders had reinforced what had once been Sera's most beautiful cities, such as Ephyra and Jacinto City, transforming them into impenetrable fortresses and securing their control with the Fortification Act.
The Human leaders knew that it was only a matter of time before Corpsers broke through the Plateau. They were proven right when the Locust emerged through the granite some ten years after Emergence Day. Jacinto Plateau was then made into yet another battlefield. Only some areas were penetrated, such as the city of Ephyra. Mankind dug in and held their position while the Lightmass Bomb was developed.
Jacinto was once the only place on Sera the Locust could not penetrate. It offered the Humans of Sera respite and safe haven from their relentless foe. However, the city of Ephyra was penetrated over the ten years after Emergence Day. After the Lightmass Bomb was activated, new cracks opened up in the granite layer, allowing deeper Locust incursions. The Locust later sank the near-Plateau cities of Tollen and Montevado very quickly. It was later discovered that this was accomplished through the use of a gargantuan worm-like creature, known as the Riftworm, that had been awakened by the Lightmass Bomb.
Originally, they intended to do this with another Lightmass Bomb, but they had to improvise and use a Lambent Brumak. The plan succeeded and Jacinto City was sunk, flooding the Hollow and apparently killing millions of the Locust Horde. It was later revealed that not all of the Locust were wiped out, but they were left severely weakened.
Later, while searching for places to evacuate the COG to, the search team did a fly-over of Jacinto City and found nothing left above ground level except the remnants of a few rail lines.