A rare crystalline element that becomes a powerful explosive when combined with an antimatter converter, obtained by the Bajoran terrorist Tahna Los to attack the wormhole.
Bilitrium appears in the Deep Space Nine episode Past Prologue. By itself it is a valuable source of energy; joined to an antimatter converter it makes a bomb of great force.
Tahna Los, a member of the extremist Kohn-Ma, takes asylum on the station with a converter already in his possession. He arranges to buy a quantity of bilitrium from the Klingon sisters Lursa and B'Etor, and Garak brings Julian Bashir in to watch the deal.
Tahna tricks Kira into flying him out in a runabout to make the exchange. His target is the mouth of the wormhole: by collapsing it he hopes to make Bajor worthless to the Federation and to Cardassia alike. Kira forces the ship through, and the device goes off harmlessly in the Gamma Quadrant.