While a physicist at Mercury Labs was building the first tachyon prototype, a speedster dressed in yellow attempted to steal the device. However, the physicist prevented this by locking the door to the prototype's chamber. Believing that the device would serve as an effective lure for the man in yellow, Barry Allen procured it from Dr. Tina McGee and brought it to S.T.A.R. Labs where Cisco Ramon, Caitlin Snow, and Eobard Thawne (as Harrison Wells) had built a trap for the man in yellow. Despite these precautions, the man in yellow managed to steal the device. Eobard later put it on the chest of his suit.
After traveling back in time and obtaining information on increasing his speed without the aid of the dangerous Velocity 9 drug, Barry went to ask Eobard for advice on how to get faster. Eobard suggested tachyon enhancement and gave Barry a flash drive containing the instructions to build a tachyon prototype. Later, Barry and his friends created their own tachyon device to enhance the Speed Force in Barry's system. While testing out the device, Barry accidentally traveled to an alternate Earth. With the aid of Supergirl's and his tachyon device, Barry made it back home. At Barry's request, Harry Wells miniaturized the device to fit behind the emblem on The Flash suit by modifying the Speed Force transmitter the former created. With Harry's enhancements from using the tachyon device, Barry was able to successfully outpace Zoom.
After Zoom captured Wally West and stole Barry's original Speed Force, Barry lost all of his speed gained from using the tachyon prototype.
Barry's tachyon device was presumably damaged or destroyed in the second particle accelerator explosion, unless it wasn't attached to his suit when they recreated the accident that originally made him a speedster. However, if the device was indeed attached to his suit (which was destroyed) during the explosion, it's possible that when he received a new suit from the Speed Force identical to the one he had before, the Speed Force may have also generated a new miniaturized tachyon device along with the rest of the suit.
After he encountered the Speed Force itself, Barry's speed was enhanced even further, so much so that he could beat Zoom without tachyon enhancement.
Nora and Barry used the tachyon unit Barry originally used to try to enhance his speed and the miniaturized version, respectively, when attempted to return Nora to the future. However, the team had to stop them, since Wally had found out (thanks to the Legends' Gideon analyzing a sample of Nora's blood) that Nora had negative tachyons in her system, which were preventing her from entering the Speed Force.
- August Heart/Godspeed
- Eobard Thawne/Reverse-Flash (formerly)
- Firestorm (modified as a Quantum splicer)
- Barry Allen/The Flash (formerly)
- Nora West-Allen/XS (formerly)
- Tachyons, according to Eobard Thawne, are superluminal particles.
- According to Eobard, if one properly harnesses tachyon particles, they can use them to move faster than light and be "invincible".