The Chief Archon was the leader of the Asgard High Council.
When Colonel Jack O'Neill attempted to solicit the Asgard's help with K'tau's sun, he informed O'Neill that the Asgard could not intervene, as it would be a violation of their treaty with the Goa'uld. (SG1: "Red Sky", "Fail Safe")
After Thor sends Hermiod to observe the humans of the Tau'ri to determine whether or not they are worthy of the Asgard legacy, the Chief Archon is one of only four members of the High Council well enough to attend the meeting. After Hermiod reports that the humans will use their technology and knowledge in war, the Chief Archon suggests that it would be better for the Asgard to leave the universe in silence with clear exhaustion in his voice. However, Hermiod reports that the humans will use the knowledge and technology in both war and peace and tells the High Council that his conclusion is that the Tau'ri are the Fifth Race and the inheritors of the Asgard legacy. This sways the Chief Archon and the High Council to go forward with the plan. (SGA: "Hermiod's Last Mission")