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The Mission to Lethia Imulsion Facility was a major operation conducted by the Coalition of Ordered Governments during the Lightmass Offensive. With the Lightmass Bomb and Sonic Resonator completed, the Coalition was in need of mapping the Hollow in order to target the Locust Horde's stronghold for the Lightmass Bomb to destroy it. The Sonic Resonator would be capable of creating a three-dimensional map of the Locust tunnels and provide targeting data in order to deliver the bomb. However, this would involve sending the Gears into the Hollow for the first time since Emergence Day and traversing enemy territory in order to gain this information. The closest access to the Hollow near Jacinto City was the Lethia Imulsion Facility. Delta-One led by Sgt. Marcus Fenix are tasked with performing this operation.


When planning the Lightmass Offensive, the Coalition concluded they needed to map the Locust tunnels first before they could launch the bomb, as to accurately pinpoint the heart of the Hollow. Thus, the Sonic Resonator was created to emit a sonic-pulse wave to create a three-dimensional map of the Locust tunnel network. Provided to Alpha-One in Ephyra, they were ordered to take it on foot to the Lethia Imulsion Facility outside the city. However, they were ambushed, and Delta-One was sent in to rescue the survivors and retrieve the Sonic Resonator, with devastating losses on their squad as well. Merged into Delta, Sgt. Marcus Fenix led Cpl. Dominic Santiago, Alpha-One survivors Pvt. Augustus Cole and Cpl. Damon Baird, and the Sonic Resonator through Ephyra. Realizing they would not make it on foot before nightfall, as the impending Kryll would soon swarm and devour anything not within light, Cpl. Santiago acquired an APC Junker fitted with Ultra-Violet Turrets from Stranded leader, Franklin Tsoko, to defend against the Kryll as they drove from Ephyra to the Lethia Imulsion Facility.

Order of Battle[]

Arriving at the Facility[]

Upon arrival in the woodland area outside of Ephyra, the Junker caught fire and broke down, forcing Delta-One to walk on foot for the remaining distance to the Lethia Imulsion Facility. Not to far, the squad arrived to the facility, only for Sgt. Fenix and Cpl. Santiago to witness "glowing" Wretches in the area. Lt. Anya Stroud informed them of numerous reports from other Gears, including Cpl. Baird and Pvt. Cole during the Destruction of Halvo Bay, of glowing Wretches that have gone Lambent, in which overexposure to Imulsion has caused them to become infected by it and glow from the same golden color as Imulsion - adding that they also explode upon death.

Reaching the main entrance of the facility, Delta-One was unable to manually open the door, and JACK would be unable to rip it open as the door was too thick. Sgt. Fenix then advised Delta-One to split up in pairs and find the entrance, against the concerns raised by Pvt. Cole. Sgt. Fenix and Cpl. Santiago went around the facility to the back loading docks while Cpl. Baird and Pvt. Cole went through the sub-levels and basement. After fighting numerous Lambent Wretches, Sgt. Fenix and Cpl. Santiago found an elevator tower, but there was no electricity in the back of the facility. Upon finding the rear generator and restoring power, the two went up the tower entrance and found an open window leading into one of the offices of the main facility.

Gaining Access Inside[]

Cpl. Baird and Pvt. Cole reached inside first through the basement while Sgt. Fenix and Cpl. Santiago had the upper levels. Cpl. Baird and Pvt. Cole navigated the basement and was ordered by Sgt. Fenix to restore power for both visibility in the facility's lights and to also power the cart control room, in which Lt. Stroud advised was the quickest route to the Imulsion mines. Upon Cpl. Baird returning power to the facility, Sgt. Fenix and Cpl. Santiago were exposed to a room full of Stranded bodies that had been recently mauled and torn apart by Lambent Wretches. The door to the cart control room was locked, but Sgt. Fenix tracked blood prints to an adjacent office where a lone Stranded survivor was awaiting rescue. Having the keys to the control room, Sgt. Fenix ordered the Stranded survivor to come with them. Cpl. Baird, at this point, been collecting Geobots that littered the facility in order to repair the Junker and requested that Sgt. Fenix find more if he could.

As the three reached their way to the cart control room, Cpl. Baird and Pvt. Cole were revealed by Lt. Stroud to be in the facility's sewer system, in which the four briefly rendezvoused at the sewer grate in the facility. Sgt. Fenix ordered each time to keep moving and meet each other at the cart control room. Navigating the facility, the Stranded survivor led Sgt. Fenix and Cpl. Santiago into the basement. However, a loose floorboard caused the Stranded survivor to fall into the sub-level and was devoured by a pack of Lambent Wretches. Traversing the loose floorboards, Sgt. Fenix and Cpl. Santiago made their way into the cart depot where they were met by more Lambent Wretches. After battling through them, the two were the reunited by Pvt. Cole and Cpl. Baird.

Imulsion Cart System[]

Upon arriving to the cart control room, Delta-One was met by a dozen guarding Drones and one Boomer, along with over a dozen Lambent Wretches. The squad neutralized the threat and entered the cart control room. Sgt. Fenix activated the cart system. The first two carts were occupied by Sgt. Fenix and Cpl. Baird, the third and fourth carts were occupied by Cpl. Santiago and Pvt. Cole. The four carts were initially headed into a furnace, but Sgt. Fenix ordered Lt. Stroud to hack into the control cart system and divert the carts to any location. The carts were then diverted through the refinery holding dozens of Lambent Wretches, Locust Drones, and Boomers.

The carts were then brought down to the ventilation area where the workers would descend from the Lethia Facility into the Imulsion mines of the Outer Hollow. Another Stranded was found within the worker's area but was in the midst of being slowly devoured by Lambent Wretches. Sgt. Fenix was able to kill the Lambent Wretches, and in their death euthanized the dying Stranded man. The four managed to reunite as Lt. Stroud brought up the elevators, which happened to be carrying Boomers. After killing the Boomers, Delta boarded the elevators as Lt. Stroud took them down, warning them to complete the mission before dawn as the Kryll would be returning soon.

Into the Outer Hollow[]

Delta arrived in the Imulsion mines of the Lethia Imulsion Facility and were directed to reach a pumping station nearby that also had an elevator that could take them topside. Sgt. Fenix ordered Cpl. Baird and Pvt. Cole, with the Sonic Resonator, to split up and find a possible short route to the pumping station while Sgt. Fenix and Cpl. Santiago looked to find another. Upon splitting up, Cpl. Baird found more Geobots within the Outer Hollow, and discovered that each Geobot contained a small, three-dimensional holographic map of the Hollow and Locust tunnels - similar to the Sonic Resonator.

Sgt. Fenix and Cpl. Santiago continued to traverse their path, but slid down an underground creek and combated more Locust Drones, Boomers, and Lambent Wretches. After the combat, Sgt. Fenix and Cpl. Santiago fell again inside a large underground sinkhole. Split up, Sgt. Fenix and Cpl. Santiago made their own way across the rock ridges and rendezvoused to a narrow cavern filled with Locust Drones and Lambent Wretches. After neutralizing the enemy and traversing the cave, Sgt. Fenix and Cpl. Santiago were met by a Corpser. Sgt. Fenix and Cpl. Santiago managed to push it back by shooting at its abdomen and face and collapsing the platform on the edge of the cliff, drowning it in Imulsion.

Battle at the Pumping Station[]

Shortly after killing the Corpser, Sgt. Fenix and Cpl. Santiago rendezvoused with Pvt. Cole and Cpl. Baird, who managed to find the pumping station ahead of the others. Walking through the caverns, Delta finally reached the pumping station but were met by Theron Guards and multiple elite Drones, aware of Delta's mission to plant the Sonic Resonator.

The four managed to repel the attack of the Theron Guard and Elite Drones, and were successful in clearing the area. After the skirmish, Cpl. Baird planted and activated the Sonic Resonator. He then joined the rest of Delta as they boarded the elevator up topside. Delta ran out of the facility to avoid the sonic blast, but were still hit and thrown by the shock wave. There were no injuries, and the Sonic Resonator was successfully deployed. However, Lt. Stroud and Col. Hoffman discovered that the Sonic Resonator did not work due to the sheer size of the Hollow.


However, Cpl. Baird then revealed one of the Geobots he discovered in the facility and showed it had more tunnel data than the resonator. Lt. Stroud then triangulated the source of the Geobot as being programmed by Professor Adam Fenix at Haldane Hall of East Barricade Academy. Col. Hoffman then ordered Sgt. Fenix to return home and retrieve any possible data from his late-father's work. Meanwhile, this intelligence was overheard by Uzil RAAM from a captured Gear before executing him. Uzil RAAM then sent a massive army at the Fenix Estate and East Barricade Academy to prevent the Coalition from obtaining Professor Fenix's data.

Locust War
0 A.E. Emergence Day (Emergence in Jannermont · Emergence in Mattino Junction · Emergence in Ilima · Emergence in Porta Ogari · Emergence in Ephyra · Fall of Gorasnaya · Evacuation of Mercy) · Battle of Nordesca · Battle of Kinnerlake · Destruction of Halvo Bay (Destruction of Old Town · Battle of the Museum of Military Glory · Siege of Halvo Bay Military Academy · Evacuation of Seahorse Hills · Battle of Elliott's Mansion · Raid on Onyx Point · Bombing of Downtown Halvo Bay · Ambush on the Halvo Bay Courthouse · Battle of the Plaza)
1 A.E. Battle of Kaia (Battle of Jasper · Battle of Autrin) · Battle of Bonbourg · Second Battle of Jannermont · Fall of Ostri · Battle of Andius · Ambush on Voslov Bridge · Hammer of Dawn Strikes · Assassination of Ukkon (Mission to CIC Aldair · Rescue of Echo-Five · Assault on Industrial District · Mission to Claybourne · Rescue of Alpha-Two · Mission to Nedroma Health Institute · Battle of Imtik Imulsion Rig · Mission to Winlock Outpost · Mission to the Badlands · Mission to Zenic Province · Battle of Ukkon's Laboratory) · Battle of Oblivion · Skirmish in the Live Zone
5 A.E. Fall of Landown
9 A.E. Battle of Noroa · Riverside Skirmish · Evacuation of Ilima (Ambush on Checkpoint Zeta · Assault on Ilima Savings and Trust · Mission to Ilima High School · Battle of Downtown Ilima · Battle of Dr. Wisen's Orphanage)
10 A.E. Battle of Estana · Skirmish at Shenko Falls · Fall of Ephyra
11 A.E. Skirmish Outside the Wire
12 A.E. Raid on Ginnet Drive · Incursions at Endeavor
13 A.E. Battle on the Andius Highway · West Barricade Campaign · Raid on the CIC
14 A.E. Operation: Midnight · Jilane Massacre · Siege of the Slab · Lightmass Offensive (Battle of Embry Square · Mission to House of Sovereigns · Ambush at Tomb of the Unknowns · Mission to Old Ephyra · Assault on Franklin's Outpost · Mission to Lethia Imulsion Facility · Mission to East Barricade Academy · Battle of Haldane Hall · Mission to Timgad · Battle on the Tyro Pillar) · Ambush at Sovereigns Boulevard · Evacuation of North Gate · Mission to Tollen · Battle of the Tollen Dam · Evacuation of Speyer · Evacuation of Fort Reval · Battle Outside of Jacinto · Mission to the Pirnah Badlands · Battle for Fucked · Mission to Montevado · Battle Near Jacinto · Unidentified M.O.U.T. Battle · Liberation of Jilane · Siege of Jacinto City · Operation: Hollow Storm (Battle of Stromson Forest · Assault on Landown · Assault on the Inner Hollow · Battle of Ilima · Destruction of the Riftworm · Mission to New Hope Research Facility · Assault on Mount Kadar · Siege of Nexus · Battle of the Royal Palace · Sinking of Jacinto City) · First Mission to Merrenat Naval Base · Skirmish South of Port Farrall · Second Mission to Merrenat Naval Base · Battle of Port Farrall · Ambush Outside of Port Farrall
15 A.E. Skirmish in the Kashkur Foothills
17 A.E. Skirmish at Endeavor · Siege of Azura · Victory Day (Attack on the Sovereign · Battle of Centennial Bridge · Ambush on Hanover Coast · Battle of the Deadlands · Battle of the Anvegad Plains · Battle of Anvil Gate · Mission to Halvo Bay · Skirmish in Concord · Mission to Mercy · Mission to Char · Battle of Endeavor · Incursions in the Serano Ocean · Battle of Azura)
Lambent War
0 B.E. Siege of the Gorgon Front · Skirmish in the South Hollow · Invasion of the Expansion Hollow · Assault on the Temple of the Trinity
0 A.E. Destruction of Old Town · Battle of the Museum of Military Glory · Battle of Elliott's Mansion · Destruction of Downtown Halvo Bay
14 A.E. Mission to Lethia Imulsion Facility · Battle on the Tyro Pillar · Siege of Nexus · Sinking of Jacinto City