The elimination of the harvesters, biological weapons from the long war between the T'Lani and the Kelleruns, after which both governments tried to kill everyone who knew how to make them.
In the Deep Space Nine episode Armageddon Game, Julian Bashir and Miles O'Brien spend a week aboard a T'Lani cruiser helping scientists from both sides find a way to destroy the last stocks of the harvesters. As the final cylinder is neutralised, Kellerun soldiers burst in and shoot the research team.
Bashir and O'Brien fight their way to a transporter and hide in a ruined complex on T'Lani III, but O'Brien has been splashed with the harvesters and sickens rapidly as Bashir tries to repair a communications set. On the station the T'Lani ambassador Sharat and the Kellerun E'Tyshra present a recording that shows both men dying in an accident.
Keiko refuses to accept it, because the recording shows Miles drinking coffee late in the day. Sisko and Dax investigate, find the runabout's logs altered and rescue the pair, tricking their pursuers into destroying an empty runabout.