Drex

Drex was a Klingon, the son of Martok and Sirella, the leaders of the House of Martok. His maternal grandfather was Linkasa. 

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.

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 that caused "serious damage to their egos".

Suspicious of their motives, 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. 

Background information
Drex was played by Obi Ndefo.

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."

Drex was mentioned in the pronunciation guide of the script of the sixth season episode. It is possible that Drex appeared or was mentioned in an early version of the script. Ultimately, much like Zek's son Krax, Drex was never seen or directly mentioned again after his first appearance.

Apocrypha
Drex appeared as first officer of the IKS Gorkon in the novel Diplomatic Implausibility, the first book of what later become a series of novels about that ship by Keith R.A. DeCandido. The captain of the Gorkon,, 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.

Drex also appears in The Left Hand of Destiny, Book One and The Left Hand of Destiny, Book Two, which are set prior to his assignment on the Gorkon.

In the story of Star Trek Online, Drex has become head of the House of Martok after Martok's apparent death and Worf serves as gin'tak for the House, advising Drex on how to successfully lead the House. Drex's son, M'ven, is the heir to the House, until he is murdered by the House of Torg and the Tal Shiar at the bat'leth competition on Forcas III.