Dillon Everett is a Colonel in the United States Marine Corps that briefly took charge of the Atlantis expedition in 2005, arriving as part of the first group of reinforcements sent from Earth via the Stargate.
Arriving with a heavily armed Marine contingent shortly before Atlantis was to come under attack by a Wraith fleet, Everett assumed command of the base by orders of Brigadier General Jack O'Neill. Initially, Everett refused to include Dr. Elizabeth Weir in discussions on the city's military defense, but relented at the insistence of Major John Sheppard. Having been a good friend of Colonel Marshall Sumner, Everett had objections to Sheppard as well, and showed little patience for the Major's at times insubordinate behavior. He also restricted the movements of Teyla Emmagan, citing concern that she might come under Wraith influence.
As the attack progressed, Everett's attitudes began to change. After Wraith soldiers had invaded the city, he allowed Teyla and the Athosians to assist in tracking them down. He also began to show respect for Weir as the Wraith siege dragged on, particularly after she secured a deal for two Genii A-bombs. (SGA: "The Siege, Part 2")
During the Wraith attack, Everett was attacked by a Wraith and fed upon. Although the Wraith was killed in mid-feeding, Everett aged considerably as a result. When Sheppard visited him in the infirmary, Everett said he had a good idea of what Sumner had gone through and that Sheppard, who shot Sumner dead to end his suffering, had done the right thing, adding that he wished Sheppard had been there to do it for him. He was returned to Earth for additional medical care. (SGA: "The Siege, Part 3")
While in Atlantis, Everett was given the Ancient Technology Activation Gene by Gene Therapy.
Upon arrival, Everett acted rather arrogant about his ability to defend Atlantis and showed an unwillingness to listen to criticism about his plans. He was also condescending and dismissive towards the civilian members of the expedition, particularly Doctor Elizabeth Weir. However, when his defenses started failing, Everett appeared to become more humble and was willing to accept outside input and help. Over time, Everett grew to respect Doctor Elizabeth Weir greatly, stating that he could think of no one better to negotiate with the Genii and promising to buy her a drink if she succeeded. Everett also began displaying respect for Weir's command of the expedition that he usurped, symbolically offering Weir her chair back and allowing Weir to address the expedition about the threat, rather than making the address himself as the commander of the base as he would've had he still been acting as he had when he arrived.
Everett greatly disliked Major John Sheppard for killing Colonel Marshall Sumner, a close friend of Everett's. Everett was angry about how Sheppard could go so far and get so close only to kill Sumner. Everett was clearly dismissive of Sheppard's belief that Sumner wished for Sheppard to kill him. After getting partially fed upon by a Wraith himself, Everett's stance on this changed and he forgave Sheppard, showing a wish for Sheppard to have been there for him as he had been for Sumner and made peace with Sheppard. (SGA: "The Siege, Part 2", "The Siege, Part 3")