Grathon Tolar

Grathon Tolar was a skilled holographic forgery artist, con-man, and general degenerate in the temporary employ of Starfleet for the ultimate purposes of bringing the Romulan Star Empire into the Dominion War on the side of the Federation.

In 2374, Tolar was awaiting execution in a Klingon prison for unspecified crimes. It was at this time when Captain Benjamin Sisko, acting under the guidance of Elim Garak and with the support of Starfleet, contacted Chancellor Gowron to arrange a pardon. Under the terms of his parole, Tolar was to stay away from the Klingon Empire and create a holo-program for Sisko. Tolar was renowned for his skills in holographic forgery which Sisko wished to put to use to create a fraudulent recording of a high-level Dominion meeting in which the supposed plan for the invasion of Romulus was discussed.

However, before Tolar could complete the recording for Sisko and Garak, he was involved in an altercation in Quark's with the proprietor and M'Pella, one of Quark's Dabo girls. Consequently, this brought the attention of station security as well as the potential for reports and documentation exposing Tolar's presence on Deep Space 9. Ultimately, Quark did not press charges against Tolar, after Captain Sisko negotiated a substantial bribe to him in exchange for his silence.

Subsequently restricted to his quarters, Tolar finished the ersatz recording and proffered it to Sisko and Garak soon afterwards. After Captain Sisko tentatively accepted the recording, he rebuffed Tolar's attempt to excuse himself -- freedom was not to be his until his recording fooled the Romulan officials it needed to fool.

Ultimately, Tolar's forgery failed to fool the Romulan senator Vreenak. After Vreenak left Deep Space 9 to expose the "vile deception" to the entire Alpha Quadrant, his shuttle exploded, killing Vreenak and his staff. An investigation by the Tal Shiar pointed to Dominion sabotage, and the recording was accepted as genuine, with the imperfections in the forgery being attributed to damage from the explosion. Known only to Sisko and Garak at the time, Garak had actually placed a bomb aboard Vreenak's shuttle, suspecting that Tolar might well not be up to the job they needed him to do. At some point, Garak also eliminated Tolar to ensure no other witnesses to the operation would remain. 

Background information
Grathon Tolar was played by actor Howard Shangraw in his only Star Trek appearance.

The script for "In the Pale Moonlight" states the pronunciation of Tolar's name is "GRAY-thun TOE-lar." Additionally, it describes him as "a small, weasel-faced ALIEN and does not look like someone who'd last very long in a Klingon prison. His clothes are clean and neatly worn, but there's a palpable oiliness to him that makes you want to bath immediately after any visit. He has a low, nervous laugh that only serves to get under Sisko's skin."

Apocrypha
Grathon Tolar is referenced in the Pocket DS9 novel Hollow Men, whereby Enderby of Starfleet Intelligence learns of Tolar's involvement in the Romulan plot, and his murder by Garak. Enderby and Jedburgh then blackmail Garak into attempting the assassination of Tomas Roeder by threatening to reveal his involvement. The novel also reveals that Captain Sisko later informs Admirals William Ross and Marta Batanides of the plot and Tolar's death.