Asgard engineer stationed aboard the Earth ship Daedalus. Hermiod's primary task is to supervise the use of Asgard technology, particularly the advanced hyperdrive that allows the Daedalus to make 18-day trips between the Milky Way and Pegasus. He is easily irritated by humans and often finds them to be a grossly unenlightened species.
Hermiod was not pleased when he was enlisted by Colonel Steven Caldwell to break the Asgard safeguards that prevented their beaming technology from transporting nuclear warheads, but since he was at the controls and the Wraith were barreling down on the ship he agreed.
Hermiod was presumably recalled when the Asgard decided to commit mass suicide, leaving their species extinct in the Milky Way Galaxy.
The Siege, Part 3 - Hermiod arrives aboard the Earth ship Daedalus to render aid to Atlantis, under siege by the Wraith.
Te Intruder - En route back to Atlantis from Earth, Hermiod locates a Wraith virus within the Daedalus computer.
Critical Mass - Hermiod modifies the Daedalus hyperdrive to reach Atlantis in time to avoid the destruction of the city.