Oa is one of the oldest planets in the universe. After the Maltusians evolved, the immigrated to Oa, a lifeless desert planet, and transformed it to serve as their base of operations as the Guardians of the Universe. Oa also serves as headquarters for the Green Lantern Corps. The power rings of fallen Lanterns can either choose a replacement or travel straight to the Guardian's chambers on Oa. For training, raw recruits are brought to Oa except those based in Frontier Space. Those receive limited instruction by their rings since travel takes too much time. The Guardians voted to deploy most of the Corps to defend against the invasion of the Red Lanterns. However, as a result, Oa was now in a vulnerable state. Atrocitus and Zilius Zox infiltrated Oa with several soldiers and attempted to kill the Guardians. Hal Jordan intervened and defeated Atrocitus. A peace was negotiated between the Guardians and Zox.
A week later, the Guardians of the Universe assigned Jordan to gather a small team to map out Manhunter hotspots. Before he embarked, Jordan recruited Kilowog away from training recruits. They then infiltrated the Science Branch to liberate Aya before she was dissected. After Aya melded to the Anti-Monitor, the Interceptor crew was recalled to Oa. Following a meeting with the council, they investigated the Science Director's quarters and discovered a hidden inner sanctum where she created Aya. After the Ranx mission, the Green Lantern Corps regrouped on Oa. After being addressed by Appa Ali Apsa, the Corps and Razer departed Oa to face Aya and the Manhunters at Maltus.