Alliance Sector Base Sigma

"She's a beauty by the Alliance, a gift, a new hope for a better future"

- An Unknown Alliance Scientist

Alliance Sector Base Sigma (ASBS) Was notified to begin construction in 2160, and finished two years later in 2162, named for its lab basics, Black Mesa Sigma. In ASBS scientist's worked to construct new weapons for the Alliance, bring new samples back from a Xen portal and decrypt any Prothean messages.

ASBS Had very few incidents, disregarding a few outbreaks it was considered a safe zone. Lorrone took up his own office residence after being brought back by the Lazarus project, observing many of the lab procedures taking place.

In 2166 Sigma had fallen under the control of the Ulyssey after the infiltration by Solaris and Ebrown. All Alliance troops surrendered control who were not killed, the rest, if any, fell back to Titan.

Lorrone was found on Sigma and committed suicide to save both commanders, claiming he was indoctrinated and under control by Tillery

"It's like Tillery is more than just a strong force...he's some kind of god"

- Ebrown on Tillery.

Ulyssey then established control over ASBS shortly after its raid. They took control of the lazarus project which was later used with the few dwindling resources to bring back Tara, a member from the Ulyssey who committed suicide to protect both Solaris and Ebrown.

After the defeat of the collectors, the newly established Systems Alliance took control of ASBS, using it for further research of project ARKCON