A Romulan assassin probe was an automated device used to kill annonymously. It was the size of a cigar and flew. These are illegal, difficult to program and find, and made of expensive material.
At the lop'no for Pok's Rite of Ascension on Taganika, Gowron brought a cha'nob to the boy; the box, however, contained a hidden assassin probe that launched against Gowron; Pok's father, Torghn, moved before him and took the hit, losing his life.
Gowron pulled the probe from Torghn's body and studied it, determining it was of Romulan origin and placed it on a table. It was picked up by the victim's brother, Qua'lon, who said that its honorless function would never be used by a Klingon, to which Gowron was sad to disagree. Vok also looked and disassembled the probe, calling it clever and effective, inciting Qua'lon, who knew that Vok was Gowron's and Torghn's enemy; he grabbed and tossed the parts of the probe down, saying that Vok had just destroyed all proofs, and killed him out of vengeance.
That night, while Pok was completing his Rite, science officer Tallot was studying the remains of the probe on the dining room's table; when the family entered, she reported her findings, determining that it was made in the Soltaris system within Romulan space. Gowron then decided to go there to seek his revenge. (ST novel: Klingon)
