In the year 2374, he was sent to negotiate with a group of Ferengi for the safe return of Ishka, the paramour of Grand Nagus Zek, in exchange for Keevan, a Vorta who had been captured by Federation Starfleet Captain Benjamin Sisko several months earlier. He agreed to meet Quark, Ishka's eldest son, and his team on the abandoned Cardassian space station, Empok Nor, but he brought along an entire platoon of Jem'Hadar soldiers as protection against the six Ferengi. He quickly got annoyed by the Ferengi's attempts to stall, however. Nevertheless, he agreed to send all of his Jem'Hadar (save two guards) away from the station as a gesture of goodwill (and to even the score to keep the Dominion from getting the drop on the Ferengi). The Ferengi had ideas other than a simple prisoner exchange, however. Yelgrun was tricked into releasing Ishka, and the two Jem'Hadar guards protecting him were killed. Yelgrun himself was captured and taken back to Deep Space 9 to be handed over to Starfleet. (DS9 episode: "The Magnificent Ferengi")
- Star Trek CCG refers to this character as "Yelgren", a spelling which contradicts the script of the episode he is in. He is also labeled as a musician, which is a subtle reference to the actor who portrays him, real-life musician Iggy Pop.