Acidium is a caustic gas Dr. Lily Pearce made from Xenomorph acid at Storr's Boon in Aliens: Fireteam Elite 2. Company scientists under Pearce developed it on LV-558 between 2204 and 2207 as a prototype chemical weapon. The tanks showed a glowing green fluid, and a finished launcher was never built. Exposure burned the throat and lungs, knocked a person out, and killed if they were not pulled away in time. Accidental short exposure left Pearce in pain, and she later built human-Engineer creatures to try to treat it.
Made From Xenomorph Acid
Pearce refined Xenomorph acid into Acidium at the Storr's Boon mine, where she was head xenobiologist in the company's hidden labs. Weyland-Yutani moved the finished gas in cylindrical tanks on colony trucks, the same glowing green fluid seen in the larger standing tanks. With no finished launcher, the plant pumped Acidium through the colony pipes toward chosen targets. In open air the cloud ran from green-yellow to orange, with a green glow and small solid specks mixed in. Smaller animals died in seconds, while a person lasted longer if they got out of the cloud in time.
Effects On Dr. Pearce
Pearce was accidentally exposed to her own gas. She treated the result as an allergic reaction, but it left her in constant pain. Her skin went pale, dark veins showed through her face, and her eyes no longer matched. One iris glowed amber. That is the look on the distress call that reached General Olivia Shipp on the UAS Endeavor. The company refused to treat her or pay her for the injury. She kept the later work from Weyland-Yutani once the company moved to take it, and she used a dead Engineer plus more than a hundred colonists to build Engineer hybrids as a treatment. She was killed in 2207 before that research produced a finished cure.
Xenomorphs In Acidium
During the Rock Bottom campaign mission, Fireteam Chimaera followed the Acidium into the Storr's Boon mines. Endeavor intel showed the gas was being pumped through the colony plumbing, the only delivery system the prototype had. Steam vents in those tunnels dumped the cloud into the air. Adult Xenomorphs crawled through that vapor under the decks, along pipes and cage lights, and they were unhurt. Their own acid does not burn them, so a gas made from that blood did not stop the hive. The cloud was leaking from the pipes, not from the later blast. Chimaera then set that plumbing to blow.
Destroyed At Storr's Boon
In the Running on Fumes campaign mission, Fireteam Chimaera triggered three self-destruct consoles in the Acidium plumbing room at Storr's Boon. The pipes detonated, and explosions tore through the industrial halls that had held the tanks. After those operations, no known samples remained, and the method for making the gas was lost with them.
After the pipes went up, the fireteam entered the buried Engineer ship and killed the remaining Engineer hybrids. In the Final Endeavor campaign mission they fought the Queen. Pearce tried to control the hive, and the Queen drove its tail through her chest. Fireteam Chimaera killed the Queen, then Shipp shot the wounded Pearce.
Conclusion
Acidium was Dr. Lily Pearce's Xenomorph-acid gas at Storr's Boon on LV-558, developed from 2204 to 2207 as a prototype chemical weapon. Exposure left her sick, she built Engineer hybrids to treat it, and Fireteam Chimaera destroyed the known stores during the 2207 campaign in Aliens: Fireteam Elite 2.
Appearances
- Aliens: Fireteam Elite 2 (2026)
Tag Categories: Alien Lore | Xenomorph Appearance
