Inverter

From Memory Alpha, the free Star Trek reference

The inverter is a folded-space transporter based on the Elway Theorem, developed for the Ansata separatists of Rutia IV. Although its repeated use led to fatal cellular degeneration, it allowed the Ansata to greatly increase the effectiveness of their terrorist campaign as the inverter could neither be tracked by sensors nor stopped by force fields. The use of the inverter leaves behind a characteristic nuclear vibration indicative of subspace transition rebound.

In 2366, the Ansata used the inverter to board the USS Enterprise-D and plant an explosive device on its warp core, as well as capturing Captain Picard. The Ansata leader Kyril Finn believed that the attack would force the Federation to mediate in their conflict with the Rutia government. The Ansata also abducted Doctor Crusher in the hopes that she could find a way to reverse the effects of the inverter. The Enterprise crew was eventually able to locate the power source of the inverter using an adaptive subspace echogram, and free Crusher and Picard. (TNG: "The High Ground")