This article is a stub and does not have enough relevant information. You can help by expanding it.

“Engineering equipment became increasingly unreliable while moving further into the Cistern. The Forerunner signal interfered with anything capable of picking it up. Engineering worked franticly to keep their equipment in running order, yet Spartan Palmer's MJOLNIR armor was able to withstand the interference.

Palmer was able to follow the signal deeper into the caves, eventually to its very source. As she got closer, the Forerunner code rippled across her sensors, translating before her very eyes. "Palmer," it said. "Help me." That was when the mission changed then from exploration to extraction.”
— Mission summary

The Source is the thirtieth and final mission of Halo: Spartan Assault.