A rare particle found in white dwarf stars, required by the intelligence that forms within the Enterprise-D's systems in order to complete the new lifeform it is building.
Vertion particles are central to the Next Generation episode Emergence. The ship begins acting by itself, laying new circuit nodes, taking over the holodeck and jumping to warp towards a white dwarf, from which it draws vertions into an object growing in a cargo bay.
The star's supply runs out before the object is finished and the construct begins to fail. On the holodeck, where the emergent mind expresses itself through a train full of characters from many programmes, the crew decide to help it and not to fight it.
La Forge proposes creating vertions artificially by firing a modified photon torpedo into the nearby MacPherson Nebula. It works: the new lifeform is completed and leaves the ship, and the Enterprise returns to normal.