In 2372, Drex was one of a large number of Klingon warriors sent to Deep Space 9 under the pretense that they were there to stand beside the Federation against the Dominion. Suspicious of their motives, Captain Benjamin Sisko ordered Lieutenant Commander Worf to investigate. Seeking to gain Martok's attention, Worf assaulted Drex in Quark's and took his d'k tahg.
Drex had a reputation for belligerence, and frequently harassed station personnel and civilians while he was at Deep Space 9. He and two accomplices were responsible for accosting Elim Garak in his shop. Garak declined to press charges, noting that he got off several remarks which caused "serious damage to their egos". (DS9: "The Way of the Warrior")
Drex was played by Obi Ndefo. He was mentioned in the pronunciation guide of the script of the sixth season episode "Sons and Daughters". It is possible that Drex appeared or was mentioned in an early version of the script.
The name "Drex" was coined by Ira Steven Behr after reading the nickname on production staffer Doug Drexler's crew jacket, and which was a source of pride for Drexler, "I got a Klingon named after me! There was a Klingon named Drex. Michael Dorn always loved my last name for a Klingon; on TNG he would yell across the stage, "Drexler, Drexler, Drexler." He'd say, "It's a great Klingon Name" And I think I told Ira that. Also I had Drex on my jacket. Ira always used to see that." (Star Trek: The Magazine Volume 1, Issue 22, p. 88)
Drex appeared as first officer of the IKS Gorkon in the novel Diplomatic Implausibility, the first book of what would later become the series of novels about that ship by Keith R.A. DeCandido. The captain of the Gorkon, Klag, was of the belief that Drex had inherited none of his father's honor, and was a detriment to the ship and its crew; he was replaced by Tereth shortly before The Brave and the Bold, Book Two.