"Funny, he said the same thing about you."
Prior to 2370, Keogh had a memorable encounter with Jadzia Dax. While both considered the other to be "arrogant," Dax believed that Keogh didn't like her, though during their "reunion", Keogh did garnish enough respect for Dax to suggest that she might serve aboard a starship, though Dax was happy with her post on Deep Space 9.
In late 2370, the Odyssey visited Deep Space 9 following a mission along the Cardassian border. By the time of his arrival, the crew of DS9 has learned of the capture of Commander Benjamin Sisko by the Jem'Hadar. Keogh was assigned the mission of entering the Gamma Quadrant and rescuing Sisko, and to investigate the threat posed by the Dominion.
The following day, accompanied by the runabouts Orinoco and Mekong, the Odyssey traveled through the Bajoran wormhole where they located the planet where Sisko was captured. As they approached the planet, they were engaged by three Jem'Hadar attack ships. Although their mission was a success and Sisko was rescued, Keogh and the rest of the Odyssey's crew were killed when a Jem'Hadar vessel made a suicide run at the ship, in an effort to send a message as to exactly how dedicated they were to maintaining their dominant stance. (DS9: "The Jem'Hadar")
The decision to destroy the Odyssey and Keogh along with it was decided upon by Deep Space Nine production staff as a way of showing the Jem'Hadar as particularly dangerous foes. "We wanted to show the long-term fans how dangerous these guys were", recalled Robert Hewitt Wolfe. "And it's my belief that had it been the Enterprise and not the Odyssey, and Picard rather than Keogh in command, that it still wouldn't have survived. Ron Moore may not agree, Patrick Stewart probably wouldn't, but it's my belief that Keogh had just as good a ship, just as good a crew, and he got smoked." (Star Trek: Deep Space Nine Companion (pp. 154-155))
Keogh may have been named after Myles Keogh, an Irish-American soldier who died at the Battle of the Little Bighorn. (Film and Television In-jokes, p 220)
The novel The Brave and the Bold, Book One gives Keogh's first name as Declan (with a nickname of "Deco") and provides an in-depth background of his character. According to the book, Keogh held the rank of lieutenant in 2346, at which time he served on the USS Lexington as chief of security where he was known as something of a womanizer and party animal. When the Lexington plays host to a diplomatic conference with the Antedians, Federation Ambassador Curzon Dax mistakenly walks in on Keogh and a female crewmember having sex. Embarrassed, and later angry when the crewmate subsequently shares a romantic encounter with Curzon, Keogh holds animosity towards Dax for years afterward.
Following this, in 2348, the Lexington travels to Altair VI to attend a presidential inauguration. Suffering a hangover after celebrating a crewmember's birthday the night before, Keogh has his assistant chief of security cover for him by beaming down to the planet. But when the assistant chief and the entire security contingent are then killed during a coup on the surface, Keogh begins to blame himself for being "young and stupid", vowing to became a more serious officer. Keogh then briefly marries a woman whom he met in 2350, though they become divorced sometime before 2370.
The novel also reveals that over the course of his career, Keogh has faced the Tzenkethi, Cardassians, Romulans, Tholians, and other races in dangerous situations. It also states that the Odyssey was his first command, having been promoted to Captain some point prior to 2365. While supporting a resettlement program on Bajor, Keogh, Kira Nerys, and Jadzia Dax were captured by the Bajoran terrorist Orta, but later rescued by the crew of Deep Space 9.
Keogh is also featured in the Star Trek Customizable Card Game.