Architect period

• The Architects discover the Kharaa Bacterium on an outer planet during a routine network expansion. A network error caused the Architects' routine quarantine procedure to fail, resulting in at least 143 billion deaths on their core worlds. The Architects quarantined their core worlds and brought Kharaa to isolated disease research facilities, including on Planet 4546B, in order to research and develop a cure.[3] The Architects construct the Quarantine Enforcement Platform, Disease Research Facility, Alien Thermal Plant, and Sanctuary Caches and began constructing Warpers (whether this was the first time Warpers were constructed is unknown). It is believed the Architects also discovered the Gargantuan Fossil around this time and began to take samples from its rib cage.
• A meteorite strikes 4546B in the Dunes biome. The resulting crater blocks the entrance to the Architect cache and the impact toppled one of the cache's pillars.
• The Architects discover the Sea Emperor Leviathan species produces Enzyme 42, a complex compound that provides immunity to Kharaa. They construct the Primary Containment Facility and Alien Arch Caches. They also capture a 1600-year-old Sea Emperor Leviathan and her seven eggs and place them in the Primary Containment Facility. It is believed the Architects also discovered the Ancient Skeleton and constructed the Lost River Laboratory Cache around this time.
• The Architects place various relics from other alien races, including humankind, in the Primary Containment Facility.
• After testing the living Sea Emperor Leviathan, the Architects discover she is too old to produce Enzyme 42 potent enough to work as a permanent cure. Instead, the Architects research the unborn eggs on the premise that a younger specimen would produce stronger enzymes. The Sea Emperor Leviathan attempts to telepathically communicate to the Architects that forcefully hatching the eggs would not work, but, according to her, "they could not hear."
• The Architects dissect a Sea Emperor Leviathan egg to study the fetus, but the process killed the fetus. They place a second egg and more eggs from other species on the planet in the Primary Containment Facility's egg lab for further research. The Architects place the remaining five Sea Emperor Leviathan eggs into the Incubator Device.