Oa himself is represented as a giant blue face, similar to an elderly man, and is situated in a section of the Universe not yet explored by man. He houses the Iron Lantern Central Battery, which can recharge not only Iron Lantern's armour but also his own Power Battery back on Earth.
However, to receive power, Oa has given Iron Lantern the task of collecting the evils of the world and bringing them to Oa so they can be absorbed into his prison levels. Oa sees Iron Lantern as his servant, but Lantern prefers to be seen as Oa's agent.
Oa also has other agents who bring him prisoners to "digest", including the future superhero, Iron Lantern 5700, Rhomann Sur (before his death), the present-day hero Tagak the Lantern-Lord, Green Guardsman (briefly) and presumably Human Lantern.