Resurrection gauntlet

The resurrection gauntlet — also known as the resurrection glove or just the glove, and, jokingly, the risen mitten — was a metal gauntlet that had the ability to revive the dead for a limited time, though with unfortunate and usually deadly consequences. There were two known gauntlets, both of which were destroyed by Torchwood Three.

Right-hand gauntlet
The right-hand gauntlet fell out of the Cardiff Space-Time Rift. (TV: They Keep Killing Suzie) It was recovered from Cardiff Bay by Torchwood Three. (TV: Dead Man Walking) It had a strange but unspecified connection to the "Life knife", as named by Ianto Jones, an alien artefact made of the same type of metal. Jack Harkness suspected the glove was not lost like most things that fell through the rift, but was disposed of, guessing the original owner wanted to be rid of it. He also could not blame them for wanting to be rid of it. (TV: They Keep Killing Suzie)

The right hand gauntlet could revive the dead, though only for a few minutes before their second, permanent death. The length of time someone came back depended on the user's empathy, in other words someone like Gwen Cooper could bring a person back for a few minutes but someone like Owen Harper would not even "get a twitch" out of a corpse. Jack put Suzie Costello in charge of testing the glove. Costello became obsessed with the possibility of being able to bring people back to life, though only for minutes at a time.

The gauntlet was more effective on recent, violent trauma victims. Suzie Costello began to murder residents of Cardiff with the Life Knife in order to improve her proficiency in using the glove. (TV: Everything Changes) She conceived an elaborate plan to use the Life Knife and the gauntlet to bring herself back from the dead, permanently. (TV: They Keep Killing Suzie)

Following the exposure of Costello as a murderer, she shot herself in the head, killing herself. The Glove was placed in Jack's safe and sealed with a "DO NOT USE" tag. (TV: Everything Changes)

Costello had already set into motion murders committed on her behalf so that Harkness would revive her, enabling her to come back to life, permanently. Gwen Cooper was the only Torchwood Three team member at that time with the degree of empathy required to operate the glove without Suzie. When the glove was used on Suzie, Gwen's life force was slowly drained from her into Suzie and she even began developing the same wound as Suzie in the back of her head where Suzie's was. Toshiko Sato destroyed the gauntlet to break the connection, saving Gwen and killing Suzie again. (TV: They Keep Killing Suzie)

Left-hand gauntlet
The left-hand gauntlet appeared in the village of Cardiff at the time when the Bubonic plague appeared in Wales, and the local people built St Mary's Church around the glove's location when they learnt of its resurrecting ability.

When a little girl, Faith, died, the local priest used the resurrection gauntlet to bring Faith back. However, Duroc subsequently used Faith as a gateway into the universe, but was sent back into the darkness before he could collect enough souls to permanently manifest. Afterwards, the glove was left locked in a box in the church.

In the early 21st century, after the death of Owen Harper, Jack used the help of a psychic to locate the left glove in order to resurrect Owen for the standard of two minutes so the team could say their goodbyes, as well as to retrieve some important Torchwood information that he possessed. However, Owen did not die after two minutes. Unlike Suzie, Owen remained clinically dead, showing no signs of life, but remained fully animate and cognitive and he was also not drawing power from Jack (the person who revived him). The team soon discovered that a strange energy was slowly transforming Owen's cell structure.

After the team learnt of the left gauntlet's connection with Duroc, they tried to stop Owen's transformation by injecting embalming fluid into his body. But the glove became animate and stopped them by attacking Martha Jones and draining her life away; leaving her at the physical age of 80. The gauntlet was then destroyed by Owen with a gunshot that reduced it to powder. (TV: Dead Man Walking)

Characteristics
Suzie's research showed that the right hand gauntlet was slightly radioactive and that the glove possessed "low psych levels" which allowed it to directly respond to brain activity. It was later established that it had an empathic link in the form of energy with its wearer, which showed up on video cameras like "a rope from [the] heart to the glove" and that it transferred the life force of the wearer into the subject to keep the latter alive. This transfer caused the glove's user to get weaker, and the subject to become stronger, until eventually the user died. The life transfer also kept the subject from dying of fatal causes such as gunshots, and the only known way to break the connection was to destroy the gauntlet; which would save the user and kill the subject again. (TV: They Keep Killing Suzie)

The left hand glove turned out to be fundamentally different from the first. Instead of using the "life force" of the wearer to resurrect the dead, it tapped into the power of Death from the afterlife to reanimate the subject. The second glove itself also seemed to be far more sinister in nature, was able to move under its own power, and possessed a limited amount of intelligence (as shown in its attack on the team when they tried to stop Duroc entering the universe); however, this may have been Duroc, from which the glove drew its power, manipulating it. (TV: Dead Man Walking) Owen Harper was resurrected by this glove, but his "living undead" state, rather than being temporary (in terms of time, or until the gauntlet was destroyed) ended up being long-term. (TV: Exit Wounds)

Torchwood website
The series 1 version of the Torchwood website showed Suzie experimenting on deceased fish with the resurrection gauntlet and the Life Knife. She noted, "Do you have any idea how hard it is cutting a tiny fish with a knife that big?"