Unending

The Asgard summon SG-1 to tell them that their experiments to halt their genetic degeneration have failed, meaning they are a dying race. Because of this, the Asgard have decided to give "everything [they] have and know" to the Tau'ri. Thor tells Colonel Carter that the people of Earth are the fifth race, the other four being the Ancients, Nox, Furlings, and the Asgard. When the Ori show up, the Asgard destroy Orilla, and themselves with it, so that their technology does not fall into the hands of the Ori. In order to preserve the Asgard legacy, Carter takes drastic action in order to prevent the Odyssey from being destroyed, along with all of the Asgard knowledge.