The appearance-stealing cord is a highly advanced piece of technology that allows Eobard Thawne to steal someone else's physical appearance.
The device originally worked with one end of the device's cords into one individual and another end into another individual, resulting the latter acclimating the former's likeness on a genetic level. Unfortunately, the host individual is corroded while the acclimated individual gets morphed into this new likeness. The process also apparently has the acclimated individual taking on the host's memories, and the acclimated individual's likeness is seemingly permanent.
A modified version of the device works the same way yet has one individual temporarily take the other individual's likeness. While changed to be nonlethal, the host individual is still caused extreme pain, and the acclimated individual's likeness can potentially return to their original likeness.
After time traveling to the year 2000 and failing to kill Barry Allen as well as being stranded in the time period, Eobard stalked Harrison Wells and Tess Morgan. After causing the couple's car crash which killed Tess, Eobard stuck one end of the device's cords into Harrison and another end into himself. As Harrison began to corrode, Eobard slowly morphed, taking on his victim's appearance and memories. Afterwards, Eobard proceeded to masquerade as Wells for nearly two decades until Eddie Thawne committed suicide which reverted Eobard's likeness before being erased from existence.
While allying himself with other villains, Eobard used the modified device to temporarily take on the appearances of Martin Stein and John Swigert. While the modified version was nonlethal, it still caused Martin extreme pain. Eobard masqueraded as Stein to infiltrate the Waverider but later vibrated his body fast enough to revert the change. To infiltrate Apollo-13, Eobard used this device to take Swigert's place of one of the crewmembers. After tranquilizing the other two astronauts, Eobard then reversed the device's effects to resume his normal appearance.
DC's Legends of Tomorrow
- In a deleted scene, Eobard tells Joe West that the device also steals the person's memories and emotions.
- Eobard's clothes didn't alter the first time and third time. However, the second time shows Eobard vibrating his body fast enough to revert the change, changing the clothes he wore. It's possible that this was because a speedster could vibrate clothing into something different.